gix-fs

Summary

A malicious tree can be constructed that will, when checked out with gitoxide, permit writing an attacker-controlled symlink into any existing directory the user has write access to.

Details

During checkout, all symlink index entries are deferred and created after regular files using a single shared gix_worktree::Stack. Internally, this uses a gix_fs::Stack.

gix_fs::Stack::make_relative_path_current() caches validated path prefixes: when the previously-processed leaf component exactly matches the leading component(s) of the next path, the leaf-to-directory transition at gix-fs/src/stack.rs:195-197 invokes only delegate.push_directory(), never delegate.push().

In gix_worktree::stack::delegate::StackDelegate, when the state member is State::CreateDirectoryAndAttributesStack, Attributes::push_directory() only loads attributes (from the ODB, in the clone case), and does not perform any other checks. The on-disk symlink_metadata() check and unlink-on-collision live in StackDelegate::push()'s invocation of create_leading_directory(), which is therefore bypassed for the cached prefix. The final symlink is created with plain std::os::unix::fs::symlink, which follows symlinks in parent directories.

Therefore, it's possible to provide a tree with duplicate symlink and directory entries that exploits this. If a tree is constructed with:

1. A 120000 (symlink) entry a that points to .git/hooks.
2. A 040000 (directory) entry a with a subtree that contains a symlink from post-checkout to ../../payload.
3. A 100755 (executable file) entry payload.

This is converted by gix_index::State::from_tree() into index entries ["a" (SYMLINK), "a/post-checkout" (SYMLINK)].

Then, during the delayed symlink phase:

1. a is created as a symlink to e.g. .git/hooks.
2. When processing a/post-checkout, the a prefix is reused from the just-processed leaf entry without re-running the intermediate-directory check, after which…
3. symlink(target, "<wt>/a/post-checkout") resolves through the just-created symlink to write .git/hooks/post-checkout.

Although this example uses .git/hooks for simplicity, there's no actual requirement to write within the repo checkout. This can be fairly easily chained into code execution by writing to something that is known to be executed — for example, by writing to .git/hooks/post-checkout if the attacker knows that a hook-aware Git implementation will be used later, or by writing to something like ~/.local/bin.

PoC

Attached is build-bad-repo.sh, which builds a repo with the aforementioned tree structure. Cloning it with gix will set up the malicious .git/hooks/post-checkout, at which point anything that normally invokes the post-checkout hook will result in its execution, such as git checkout -b new-branch.

Impact

Arbitrary symlink creation into any existing directory the user can write to.

Disclosure

This vulnerability was found by AI (specifically, Claude Mythos) as part of Project Glasswing. This advisory was written and verified by a human.

Summary

A malicious tree can be constructed that will, when checked out with gitoxide, permit writing an attacker-controlled symlink into any existing directory the user has write access to.

Details

During checkout, all symlink index entries are deferred and created after regular files using a single shared gix_worktree::Stack. Internally, this uses a gix_fs::Stack.

gix_fs::Stack::make_relative_path_current() caches validated path prefixes: when the previously-processed leaf component exactly matches the leading component(s) of the next path, the leaf-to-directory transition at gix-fs/src/stack.rs:195-197 invokes only delegate.push_directory(), never delegate.push().

In gix_worktree::stack::delegate::StackDelegate, when the state member is State::CreateDirectoryAndAttributesStack, Attributes::push_directory() only loads attributes (from the ODB, in the clone case), and does not perform any other checks. The on-disk symlink_metadata() check and unlink-on-collision live in StackDelegate::push()'s invocation of create_leading_directory(), which is therefore bypassed for the cached prefix. The final symlink is created with plain std::os::unix::fs::symlink, which follows symlinks in parent directories.

Therefore, it's possible to provide a tree with duplicate symlink and directory entries that exploits this. If a tree is constructed with:

1. A 120000 (symlink) entry a that points to .git/hooks.
2. A 040000 (directory) entry a with a subtree that contains a symlink from post-checkout to ../../payload.
3. A 100755 (executable file) entry payload.

This is converted by gix_index::State::from_tree() into index entries ["a" (SYMLINK), "a/post-checkout" (SYMLINK)].

Then, during the delayed symlink phase:

1. a is created as a symlink to e.g. .git/hooks.
2. When processing a/post-checkout, the a prefix is reused from the just-processed leaf entry without re-running the intermediate-directory check, after which…
3. symlink(target, "<wt>/a/post-checkout") resolves through the just-created symlink to write .git/hooks/post-checkout.

Although this example uses .git/hooks for simplicity, there's no actual requirement to write within the repo checkout. This can be fairly easily chained into code execution by writing to something that is known to be executed — for example, by writing to .git/hooks/post-checkout if the attacker knows that a hook-aware Git implementation will be used later, or by writing to something like ~/.local/bin.

PoC

Attached is build-bad-repo.sh, which builds a repo with the aforementioned tree structure. Cloning it with gix will set up the malicious .git/hooks/post-checkout, at which point anything that normally invokes the post-checkout hook will result in its execution, such as git checkout -b new-branch.

Impact

Arbitrary symlink creation into any existing directory the user can write to.

Disclosure

This vulnerability was found by AI (specifically, Claude Mythos) as part of Project Glasswing. This advisory was written and verified by a human.

Summary

A malicious tree can be constructed that will, when checked out with gitoxide, permit writing an attacker-controlled symlink into any existing directory the user has write access to.

Details

During checkout, all symlink index entries are deferred and created after regular files using a single shared gix_worktree::Stack. Internally, this uses a gix_fs::Stack.

gix_fs::Stack::make_relative_path_current() caches validated path prefixes: when the previously-processed leaf component exactly matches the leading component(s) of the next path, the leaf-to-directory transition at gix-fs/src/stack.rs:195-197 invokes only delegate.push_directory(), never delegate.push().

In gix_worktree::stack::delegate::StackDelegate, when the state member is State::CreateDirectoryAndAttributesStack, Attributes::push_directory() only loads attributes (from the ODB, in the clone case), and does not perform any other checks. The on-disk symlink_metadata() check and unlink-on-collision live in StackDelegate::push()'s invocation of create_leading_directory(), which is therefore bypassed for the cached prefix. The final symlink is created with plain std::os::unix::fs::symlink, which follows symlinks in parent directories.

Therefore, it's possible to provide a tree with duplicate symlink and directory entries that exploits this. If a tree is constructed with:

1. A 120000 (symlink) entry a that points to .git/hooks.
2. A 040000 (directory) entry a with a subtree that contains a symlink from post-checkout to ../../payload.
3. A 100755 (executable file) entry payload.

This is converted by gix_index::State::from_tree() into index entries ["a" (SYMLINK), "a/post-checkout" (SYMLINK)].

Then, during the delayed symlink phase:

1. a is created as a symlink to e.g. .git/hooks.
2. When processing a/post-checkout, the a prefix is reused from the just-processed leaf entry without re-running the intermediate-directory check, after which…
3. symlink(target, "<wt>/a/post-checkout") resolves through the just-created symlink to write .git/hooks/post-checkout.

Although this example uses .git/hooks for simplicity, there's no actual requirement to write within the repo checkout. This can be fairly easily chained into code execution by writing to something that is known to be executed — for example, by writing to .git/hooks/post-checkout if the attacker knows that a hook-aware Git implementation will be used later, or by writing to something like ~/.local/bin.

PoC

Attached is build-bad-repo.sh, which builds a repo with the aforementioned tree structure. Cloning it with gix will set up the malicious .git/hooks/post-checkout, at which point anything that normally invokes the post-checkout hook will result in its execution, such as git checkout -b new-branch.

Impact

Arbitrary symlink creation into any existing directory the user can write to.

Disclosure

This vulnerability was found by AI (specifically, Claude Mythos) as part of Project Glasswing. This advisory was written and verified by a human.

Summary

A malicious tree can be constructed that will, when checked out with gitoxide, permit writing an attacker-controlled symlink into any existing directory the user has write access to.

Details

During checkout, all symlink index entries are deferred and created after regular files using a single shared gix_worktree::Stack. Internally, this uses a gix_fs::Stack.

gix_fs::Stack::make_relative_path_current() caches validated path prefixes: when the previously-processed leaf component exactly matches the leading component(s) of the next path, the leaf-to-directory transition at gix-fs/src/stack.rs:195-197 invokes only delegate.push_directory(), never delegate.push().

In gix_worktree::stack::delegate::StackDelegate, when the state member is State::CreateDirectoryAndAttributesStack, Attributes::push_directory() only loads attributes (from the ODB, in the clone case), and does not perform any other checks. The on-disk symlink_metadata() check and unlink-on-collision live in StackDelegate::push()'s invocation of create_leading_directory(), which is therefore bypassed for the cached prefix. The final symlink is created with plain std::os::unix::fs::symlink, which follows symlinks in parent directories.

Therefore, it's possible to provide a tree with duplicate symlink and directory entries that exploits this. If a tree is constructed with:

1. A 120000 (symlink) entry a that points to .git/hooks.
2. A 040000 (directory) entry a with a subtree that contains a symlink from post-checkout to ../../payload.
3. A 100755 (executable file) entry payload.

This is converted by gix_index::State::from_tree() into index entries ["a" (SYMLINK), "a/post-checkout" (SYMLINK)].

Then, during the delayed symlink phase:

1. a is created as a symlink to e.g. .git/hooks.
2. When processing a/post-checkout, the a prefix is reused from the just-processed leaf entry without re-running the intermediate-directory check, after which…
3. symlink(target, "<wt>/a/post-checkout") resolves through the just-created symlink to write .git/hooks/post-checkout.

Although this example uses .git/hooks for simplicity, there's no actual requirement to write within the repo checkout. This can be fairly easily chained into code execution by writing to something that is known to be executed — for example, by writing to .git/hooks/post-checkout if the attacker knows that a hook-aware Git implementation will be used later, or by writing to something like ~/.local/bin.

PoC

Attached is build-bad-repo.sh, which builds a repo with the aforementioned tree structure. Cloning it with gix will set up the malicious .git/hooks/post-checkout, at which point anything that normally invokes the post-checkout hook will result in its execution, such as git checkout -b new-branch.

Impact

Arbitrary symlink creation into any existing directory the user can write to.

Disclosure

This vulnerability was found by AI (specifically, Claude Mythos) as part of Project Glasswing. This advisory was written and verified by a human.

Summary

A malicious tree can be constructed that will, when checked out with gitoxide, permit writing an attacker-controlled symlink into any existing directory the user has write access to.

Details

During checkout, all symlink index entries are deferred and created after regular files using a single shared gix_worktree::Stack. Internally, this uses a gix_fs::Stack.

gix_fs::Stack::make_relative_path_current() caches validated path prefixes: when the previously-processed leaf component exactly matches the leading component(s) of the next path, the leaf-to-directory transition at gix-fs/src/stack.rs:195-197 invokes only delegate.push_directory(), never delegate.push().

In gix_worktree::stack::delegate::StackDelegate, when the state member is State::CreateDirectoryAndAttributesStack, Attributes::push_directory() only loads attributes (from the ODB, in the clone case), and does not perform any other checks. The on-disk symlink_metadata() check and unlink-on-collision live in StackDelegate::push()'s invocation of create_leading_directory(), which is therefore bypassed for the cached prefix. The final symlink is created with plain std::os::unix::fs::symlink, which follows symlinks in parent directories.

Therefore, it's possible to provide a tree with duplicate symlink and directory entries that exploits this. If a tree is constructed with:

1. A 120000 (symlink) entry a that points to .git/hooks.
2. A 040000 (directory) entry a with a subtree that contains a symlink from post-checkout to ../../payload.
3. A 100755 (executable file) entry payload.

This is converted by gix_index::State::from_tree() into index entries ["a" (SYMLINK), "a/post-checkout" (SYMLINK)].

Then, during the delayed symlink phase:

1. a is created as a symlink to e.g. .git/hooks.
2. When processing a/post-checkout, the a prefix is reused from the just-processed leaf entry without re-running the intermediate-directory check, after which…
3. symlink(target, "<wt>/a/post-checkout") resolves through the just-created symlink to write .git/hooks/post-checkout.

Although this example uses .git/hooks for simplicity, there's no actual requirement to write within the repo checkout. This can be fairly easily chained into code execution by writing to something that is known to be executed — for example, by writing to .git/hooks/post-checkout if the attacker knows that a hook-aware Git implementation will be used later, or by writing to something like ~/.local/bin.

PoC

Attached is build-bad-repo.sh, which builds a repo with the aforementioned tree structure. Cloning it with gix will set up the malicious .git/hooks/post-checkout, at which point anything that normally invokes the post-checkout hook will result in its execution, such as git checkout -b new-branch.

Impact

Arbitrary symlink creation into any existing directory the user can write to.

Disclosure

This vulnerability was found by AI (specifically, Claude Mythos) as part of Project Glasswing. This advisory was written and verified by a human.

Summary

A malicious tree can be constructed that will, when checked out with gitoxide, permit writing an attacker-controlled symlink into any existing directory the user has write access to.

Details

During checkout, all symlink index entries are deferred and created after regular files using a single shared gix_worktree::Stack. Internally, this uses a gix_fs::Stack.

gix_fs::Stack::make_relative_path_current() caches validated path prefixes: when the previously-processed leaf component exactly matches the leading component(s) of the next path, the leaf-to-directory transition at gix-fs/src/stack.rs:195-197 invokes only delegate.push_directory(), never delegate.push().

In gix_worktree::stack::delegate::StackDelegate, when the state member is State::CreateDirectoryAndAttributesStack, Attributes::push_directory() only loads attributes (from the ODB, in the clone case), and does not perform any other checks. The on-disk symlink_metadata() check and unlink-on-collision live in StackDelegate::push()'s invocation of create_leading_directory(), which is therefore bypassed for the cached prefix. The final symlink is created with plain std::os::unix::fs::symlink, which follows symlinks in parent directories.

Therefore, it's possible to provide a tree with duplicate symlink and directory entries that exploits this. If a tree is constructed with:

1. A 120000 (symlink) entry a that points to .git/hooks.
2. A 040000 (directory) entry a with a subtree that contains a symlink from post-checkout to ../../payload.
3. A 100755 (executable file) entry payload.

This is converted by gix_index::State::from_tree() into index entries ["a" (SYMLINK), "a/post-checkout" (SYMLINK)].

Then, during the delayed symlink phase:

1. a is created as a symlink to e.g. .git/hooks.
2. When processing a/post-checkout, the a prefix is reused from the just-processed leaf entry without re-running the intermediate-directory check, after which…
3. symlink(target, "<wt>/a/post-checkout") resolves through the just-created symlink to write .git/hooks/post-checkout.

Although this example uses .git/hooks for simplicity, there's no actual requirement to write within the repo checkout. This can be fairly easily chained into code execution by writing to something that is known to be executed — for example, by writing to .git/hooks/post-checkout if the attacker knows that a hook-aware Git implementation will be used later, or by writing to something like ~/.local/bin.

PoC

Attached is build-bad-repo.sh, which builds a repo with the aforementioned tree structure. Cloning it with gix will set up the malicious .git/hooks/post-checkout, at which point anything that normally invokes the post-checkout hook will result in its execution, such as git checkout -b new-branch.

Impact

Arbitrary symlink creation into any existing directory the user can write to.

Disclosure

This vulnerability was found by AI (specifically, Claude Mythos) as part of Project Glasswing. This advisory was written and verified by a human.

Summary

A malicious tree can be constructed that will, when checked out with gitoxide, permit writing an attacker-controlled symlink into any existing directory the user has write access to.

Details

During checkout, all symlink index entries are deferred and created after regular files using a single shared gix_worktree::Stack. Internally, this uses a gix_fs::Stack.

gix_fs::Stack::make_relative_path_current() caches validated path prefixes: when the previously-processed leaf component exactly matches the leading component(s) of the next path, the leaf-to-directory transition at gix-fs/src/stack.rs:195-197 invokes only delegate.push_directory(), never delegate.push().

In gix_worktree::stack::delegate::StackDelegate, when the state member is State::CreateDirectoryAndAttributesStack, Attributes::push_directory() only loads attributes (from the ODB, in the clone case), and does not perform any other checks. The on-disk symlink_metadata() check and unlink-on-collision live in StackDelegate::push()'s invocation of create_leading_directory(), which is therefore bypassed for the cached prefix. The final symlink is created with plain std::os::unix::fs::symlink, which follows symlinks in parent directories.

Therefore, it's possible to provide a tree with duplicate symlink and directory entries that exploits this. If a tree is constructed with:

1. A 120000 (symlink) entry a that points to .git/hooks.
2. A 040000 (directory) entry a with a subtree that contains a symlink from post-checkout to ../../payload.
3. A 100755 (executable file) entry payload.

This is converted by gix_index::State::from_tree() into index entries ["a" (SYMLINK), "a/post-checkout" (SYMLINK)].

Then, during the delayed symlink phase:

1. a is created as a symlink to e.g. .git/hooks.
2. When processing a/post-checkout, the a prefix is reused from the just-processed leaf entry without re-running the intermediate-directory check, after which…
3. symlink(target, "<wt>/a/post-checkout") resolves through the just-created symlink to write .git/hooks/post-checkout.

Although this example uses .git/hooks for simplicity, there's no actual requirement to write within the repo checkout. This can be fairly easily chained into code execution by writing to something that is known to be executed — for example, by writing to .git/hooks/post-checkout if the attacker knows that a hook-aware Git implementation will be used later, or by writing to something like ~/.local/bin.

PoC

Attached is build-bad-repo.sh, which builds a repo with the aforementioned tree structure. Cloning it with gix will set up the malicious .git/hooks/post-checkout, at which point anything that normally invokes the post-checkout hook will result in its execution, such as git checkout -b new-branch.

Impact

Arbitrary symlink creation into any existing directory the user can write to.

Disclosure

This vulnerability was found by AI (specifically, Claude Mythos) as part of Project Glasswing. This advisory was written and verified by a human.

Summary

A malicious tree can be constructed that will, when checked out with gitoxide, permit writing an attacker-controlled symlink into any existing directory the user has write access to.

Details

During checkout, all symlink index entries are deferred and created after regular files using a single shared gix_worktree::Stack. Internally, this uses a gix_fs::Stack.

gix_fs::Stack::make_relative_path_current() caches validated path prefixes: when the previously-processed leaf component exactly matches the leading component(s) of the next path, the leaf-to-directory transition at gix-fs/src/stack.rs:195-197 invokes only delegate.push_directory(), never delegate.push().

In gix_worktree::stack::delegate::StackDelegate, when the state member is State::CreateDirectoryAndAttributesStack, Attributes::push_directory() only loads attributes (from the ODB, in the clone case), and does not perform any other checks. The on-disk symlink_metadata() check and unlink-on-collision live in StackDelegate::push()'s invocation of create_leading_directory(), which is therefore bypassed for the cached prefix. The final symlink is created with plain std::os::unix::fs::symlink, which follows symlinks in parent directories.

Therefore, it's possible to provide a tree with duplicate symlink and directory entries that exploits this. If a tree is constructed with:

1. A 120000 (symlink) entry a that points to .git/hooks.
2. A 040000 (directory) entry a with a subtree that contains a symlink from post-checkout to ../../payload.
3. A 100755 (executable file) entry payload.

This is converted by gix_index::State::from_tree() into index entries ["a" (SYMLINK), "a/post-checkout" (SYMLINK)].

Then, during the delayed symlink phase:

1. a is created as a symlink to e.g. .git/hooks.
2. When processing a/post-checkout, the a prefix is reused from the just-processed leaf entry without re-running the intermediate-directory check, after which…
3. symlink(target, "<wt>/a/post-checkout") resolves through the just-created symlink to write .git/hooks/post-checkout.

Although this example uses .git/hooks for simplicity, there's no actual requirement to write within the repo checkout. This can be fairly easily chained into code execution by writing to something that is known to be executed — for example, by writing to .git/hooks/post-checkout if the attacker knows that a hook-aware Git implementation will be used later, or by writing to something like ~/.local/bin.

PoC

Attached is build-bad-repo.sh, which builds a repo with the aforementioned tree structure. Cloning it with gix will set up the malicious .git/hooks/post-checkout, at which point anything that normally invokes the post-checkout hook will result in its execution, such as git checkout -b new-branch.

Impact

Arbitrary symlink creation into any existing directory the user can write to.

Disclosure

This vulnerability was found by AI (specifically, Claude Mythos) as part of Project Glasswing. This advisory was written and verified by a human.

Summary

A malicious tree can be constructed that will, when checked out with gitoxide, permit writing an attacker-controlled symlink into any existing directory the user has write access to.

Details

During checkout, all symlink index entries are deferred and created after regular files using a single shared gix_worktree::Stack. Internally, this uses a gix_fs::Stack.

gix_fs::Stack::make_relative_path_current() caches validated path prefixes: when the previously-processed leaf component exactly matches the leading component(s) of the next path, the leaf-to-directory transition at gix-fs/src/stack.rs:195-197 invokes only delegate.push_directory(), never delegate.push().

In gix_worktree::stack::delegate::StackDelegate, when the state member is State::CreateDirectoryAndAttributesStack, Attributes::push_directory() only loads attributes (from the ODB, in the clone case), and does not perform any other checks. The on-disk symlink_metadata() check and unlink-on-collision live in StackDelegate::push()'s invocation of create_leading_directory(), which is therefore bypassed for the cached prefix. The final symlink is created with plain std::os::unix::fs::symlink, which follows symlinks in parent directories.

Therefore, it's possible to provide a tree with duplicate symlink and directory entries that exploits this. If a tree is constructed with:

1. A 120000 (symlink) entry a that points to .git/hooks.
2. A 040000 (directory) entry a with a subtree that contains a symlink from post-checkout to ../../payload.
3. A 100755 (executable file) entry payload.

This is converted by gix_index::State::from_tree() into index entries ["a" (SYMLINK), "a/post-checkout" (SYMLINK)].

Then, during the delayed symlink phase:

1. a is created as a symlink to e.g. .git/hooks.
2. When processing a/post-checkout, the a prefix is reused from the just-processed leaf entry without re-running the intermediate-directory check, after which…
3. symlink(target, "<wt>/a/post-checkout") resolves through the just-created symlink to write .git/hooks/post-checkout.

Although this example uses .git/hooks for simplicity, there's no actual requirement to write within the repo checkout. This can be fairly easily chained into code execution by writing to something that is known to be executed — for example, by writing to .git/hooks/post-checkout if the attacker knows that a hook-aware Git implementation will be used later, or by writing to something like ~/.local/bin.

PoC

Attached is build-bad-repo.sh, which builds a repo with the aforementioned tree structure. Cloning it with gix will set up the malicious .git/hooks/post-checkout, at which point anything that normally invokes the post-checkout hook will result in its execution, such as git checkout -b new-branch.

Impact

Arbitrary symlink creation into any existing directory the user can write to.

Disclosure

This vulnerability was found by AI (specifically, Claude Mythos) as part of Project Glasswing. This advisory was written and verified by a human.

Summary

A malicious tree can be constructed that will, when checked out with gitoxide, permit writing an attacker-controlled symlink into any existing directory the user has write access to.

Details

During checkout, all symlink index entries are deferred and created after regular files using a single shared gix_worktree::Stack. Internally, this uses a gix_fs::Stack.

gix_fs::Stack::make_relative_path_current() caches validated path prefixes: when the previously-processed leaf component exactly matches the leading component(s) of the next path, the leaf-to-directory transition at gix-fs/src/stack.rs:195-197 invokes only delegate.push_directory(), never delegate.push().

In gix_worktree::stack::delegate::StackDelegate, when the state member is State::CreateDirectoryAndAttributesStack, Attributes::push_directory() only loads attributes (from the ODB, in the clone case), and does not perform any other checks. The on-disk symlink_metadata() check and unlink-on-collision live in StackDelegate::push()'s invocation of create_leading_directory(), which is therefore bypassed for the cached prefix. The final symlink is created with plain std::os::unix::fs::symlink, which follows symlinks in parent directories.

Therefore, it's possible to provide a tree with duplicate symlink and directory entries that exploits this. If a tree is constructed with:

1. A 120000 (symlink) entry a that points to .git/hooks.
2. A 040000 (directory) entry a with a subtree that contains a symlink from post-checkout to ../../payload.
3. A 100755 (executable file) entry payload.

This is converted by gix_index::State::from_tree() into index entries ["a" (SYMLINK), "a/post-checkout" (SYMLINK)].

Then, during the delayed symlink phase:

1. a is created as a symlink to e.g. .git/hooks.
2. When processing a/post-checkout, the a prefix is reused from the just-processed leaf entry without re-running the intermediate-directory check, after which…
3. symlink(target, "<wt>/a/post-checkout") resolves through the just-created symlink to write .git/hooks/post-checkout.

Although this example uses .git/hooks for simplicity, there's no actual requirement to write within the repo checkout. This can be fairly easily chained into code execution by writing to something that is known to be executed — for example, by writing to .git/hooks/post-checkout if the attacker knows that a hook-aware Git implementation will be used later, or by writing to something like ~/.local/bin.

PoC

Attached is build-bad-repo.sh, which builds a repo with the aforementioned tree structure. Cloning it with gix will set up the malicious .git/hooks/post-checkout, at which point anything that normally invokes the post-checkout hook will result in its execution, such as git checkout -b new-branch.

Impact

Arbitrary symlink creation into any existing directory the user can write to.

Disclosure

This vulnerability was found by AI (specifically, Claude Mythos) as part of Project Glasswing. This advisory was written and verified by a human.

Summary

A malicious tree can be constructed that will, when checked out with gitoxide, permit writing an attacker-controlled symlink into any existing directory the user has write access to.

Details

During checkout, all symlink index entries are deferred and created after regular files using a single shared gix_worktree::Stack. Internally, this uses a gix_fs::Stack.

gix_fs::Stack::make_relative_path_current() caches validated path prefixes: when the previously-processed leaf component exactly matches the leading component(s) of the next path, the leaf-to-directory transition at gix-fs/src/stack.rs:195-197 invokes only delegate.push_directory(), never delegate.push().

In gix_worktree::stack::delegate::StackDelegate, when the state member is State::CreateDirectoryAndAttributesStack, Attributes::push_directory() only loads attributes (from the ODB, in the clone case), and does not perform any other checks. The on-disk symlink_metadata() check and unlink-on-collision live in StackDelegate::push()'s invocation of create_leading_directory(), which is therefore bypassed for the cached prefix. The final symlink is created with plain std::os::unix::fs::symlink, which follows symlinks in parent directories.

Therefore, it's possible to provide a tree with duplicate symlink and directory entries that exploits this. If a tree is constructed with:

1. A 120000 (symlink) entry a that points to .git/hooks.
2. A 040000 (directory) entry a with a subtree that contains a symlink from post-checkout to ../../payload.
3. A 100755 (executable file) entry payload.

This is converted by gix_index::State::from_tree() into index entries ["a" (SYMLINK), "a/post-checkout" (SYMLINK)].

Then, during the delayed symlink phase:

1. a is created as a symlink to e.g. .git/hooks.
2. When processing a/post-checkout, the a prefix is reused from the just-processed leaf entry without re-running the intermediate-directory check, after which…
3. symlink(target, "<wt>/a/post-checkout") resolves through the just-created symlink to write .git/hooks/post-checkout.

Although this example uses .git/hooks for simplicity, there's no actual requirement to write within the repo checkout. This can be fairly easily chained into code execution by writing to something that is known to be executed — for example, by writing to .git/hooks/post-checkout if the attacker knows that a hook-aware Git implementation will be used later, or by writing to something like ~/.local/bin.

PoC

Attached is build-bad-repo.sh, which builds a repo with the aforementioned tree structure. Cloning it with gix will set up the malicious .git/hooks/post-checkout, at which point anything that normally invokes the post-checkout hook will result in its execution, such as git checkout -b new-branch.

Impact

Arbitrary symlink creation into any existing directory the user can write to.

Disclosure

This vulnerability was found by AI (specifically, Claude Mythos) as part of Project Glasswing. This advisory was written and verified by a human.

Summary

A malicious tree can be constructed that will, when checked out with gitoxide, permit writing an attacker-controlled symlink into any existing directory the user has write access to.

Details

During checkout, all symlink index entries are deferred and created after regular files using a single shared gix_worktree::Stack. Internally, this uses a gix_fs::Stack.

gix_fs::Stack::make_relative_path_current() caches validated path prefixes: when the previously-processed leaf component exactly matches the leading component(s) of the next path, the leaf-to-directory transition at gix-fs/src/stack.rs:195-197 invokes only delegate.push_directory(), never delegate.push().

In gix_worktree::stack::delegate::StackDelegate, when the state member is State::CreateDirectoryAndAttributesStack, Attributes::push_directory() only loads attributes (from the ODB, in the clone case), and does not perform any other checks. The on-disk symlink_metadata() check and unlink-on-collision live in StackDelegate::push()'s invocation of create_leading_directory(), which is therefore bypassed for the cached prefix. The final symlink is created with plain std::os::unix::fs::symlink, which follows symlinks in parent directories.

Therefore, it's possible to provide a tree with duplicate symlink and directory entries that exploits this. If a tree is constructed with:

1. A 120000 (symlink) entry a that points to .git/hooks.
2. A 040000 (directory) entry a with a subtree that contains a symlink from post-checkout to ../../payload.
3. A 100755 (executable file) entry payload.

This is converted by gix_index::State::from_tree() into index entries ["a" (SYMLINK), "a/post-checkout" (SYMLINK)].

Then, during the delayed symlink phase:

1. a is created as a symlink to e.g. .git/hooks.
2. When processing a/post-checkout, the a prefix is reused from the just-processed leaf entry without re-running the intermediate-directory check, after which…
3. symlink(target, "<wt>/a/post-checkout") resolves through the just-created symlink to write .git/hooks/post-checkout.

Although this example uses .git/hooks for simplicity, there's no actual requirement to write within the repo checkout. This can be fairly easily chained into code execution by writing to something that is known to be executed — for example, by writing to .git/hooks/post-checkout if the attacker knows that a hook-aware Git implementation will be used later, or by writing to something like ~/.local/bin.

PoC

Attached is build-bad-repo.sh, which builds a repo with the aforementioned tree structure. Cloning it with gix will set up the malicious .git/hooks/post-checkout, at which point anything that normally invokes the post-checkout hook will result in its execution, such as git checkout -b new-branch.

Impact

Arbitrary symlink creation into any existing directory the user can write to.

Disclosure

This vulnerability was found by AI (specifically, Claude Mythos) as part of Project Glasswing. This advisory was written and verified by a human.

Summary

A malicious tree can be constructed that will, when checked out with gitoxide, permit writing an attacker-controlled symlink into any existing directory the user has write access to.

Details

During checkout, all symlink index entries are deferred and created after regular files using a single shared gix_worktree::Stack. Internally, this uses a gix_fs::Stack.

gix_fs::Stack::make_relative_path_current() caches validated path prefixes: when the previously-processed leaf component exactly matches the leading component(s) of the next path, the leaf-to-directory transition at gix-fs/src/stack.rs:195-197 invokes only delegate.push_directory(), never delegate.push().

In gix_worktree::stack::delegate::StackDelegate, when the state member is State::CreateDirectoryAndAttributesStack, Attributes::push_directory() only loads attributes (from the ODB, in the clone case), and does not perform any other checks. The on-disk symlink_metadata() check and unlink-on-collision live in StackDelegate::push()'s invocation of create_leading_directory(), which is therefore bypassed for the cached prefix. The final symlink is created with plain std::os::unix::fs::symlink, which follows symlinks in parent directories.

Therefore, it's possible to provide a tree with duplicate symlink and directory entries that exploits this. If a tree is constructed with:

1. A 120000 (symlink) entry a that points to .git/hooks.
2. A 040000 (directory) entry a with a subtree that contains a symlink from post-checkout to ../../payload.
3. A 100755 (executable file) entry payload.

This is converted by gix_index::State::from_tree() into index entries ["a" (SYMLINK), "a/post-checkout" (SYMLINK)].

Then, during the delayed symlink phase:

1. a is created as a symlink to e.g. .git/hooks.
2. When processing a/post-checkout, the a prefix is reused from the just-processed leaf entry without re-running the intermediate-directory check, after which…
3. symlink(target, "<wt>/a/post-checkout") resolves through the just-created symlink to write .git/hooks/post-checkout.

Although this example uses .git/hooks for simplicity, there's no actual requirement to write within the repo checkout. This can be fairly easily chained into code execution by writing to something that is known to be executed — for example, by writing to .git/hooks/post-checkout if the attacker knows that a hook-aware Git implementation will be used later, or by writing to something like ~/.local/bin.

PoC

Attached is build-bad-repo.sh, which builds a repo with the aforementioned tree structure. Cloning it with gix will set up the malicious .git/hooks/post-checkout, at which point anything that normally invokes the post-checkout hook will result in its execution, such as git checkout -b new-branch.

Impact

Arbitrary symlink creation into any existing directory the user can write to.

Disclosure

This vulnerability was found by AI (specifically, Claude Mythos) as part of Project Glasswing. This advisory was written and verified by a human.

Summary

A malicious tree can be constructed that will, when checked out with gitoxide, permit writing an attacker-controlled symlink into any existing directory the user has write access to.

Details

During checkout, all symlink index entries are deferred and created after regular files using a single shared gix_worktree::Stack. Internally, this uses a gix_fs::Stack.

gix_fs::Stack::make_relative_path_current() caches validated path prefixes: when the previously-processed leaf component exactly matches the leading component(s) of the next path, the leaf-to-directory transition at gix-fs/src/stack.rs:195-197 invokes only delegate.push_directory(), never delegate.push().

In gix_worktree::stack::delegate::StackDelegate, when the state member is State::CreateDirectoryAndAttributesStack, Attributes::push_directory() only loads attributes (from the ODB, in the clone case), and does not perform any other checks. The on-disk symlink_metadata() check and unlink-on-collision live in StackDelegate::push()'s invocation of create_leading_directory(), which is therefore bypassed for the cached prefix. The final symlink is created with plain std::os::unix::fs::symlink, which follows symlinks in parent directories.

Therefore, it's possible to provide a tree with duplicate symlink and directory entries that exploits this. If a tree is constructed with:

1. A 120000 (symlink) entry a that points to .git/hooks.
2. A 040000 (directory) entry a with a subtree that contains a symlink from post-checkout to ../../payload.
3. A 100755 (executable file) entry payload.

This is converted by gix_index::State::from_tree() into index entries ["a" (SYMLINK), "a/post-checkout" (SYMLINK)].

Then, during the delayed symlink phase:

1. a is created as a symlink to e.g. .git/hooks.
2. When processing a/post-checkout, the a prefix is reused from the just-processed leaf entry without re-running the intermediate-directory check, after which…
3. symlink(target, "<wt>/a/post-checkout") resolves through the just-created symlink to write .git/hooks/post-checkout.

Although this example uses .git/hooks for simplicity, there's no actual requirement to write within the repo checkout. This can be fairly easily chained into code execution by writing to something that is known to be executed — for example, by writing to .git/hooks/post-checkout if the attacker knows that a hook-aware Git implementation will be used later, or by writing to something like ~/.local/bin.

PoC

Attached is build-bad-repo.sh, which builds a repo with the aforementioned tree structure. Cloning it with gix will set up the malicious .git/hooks/post-checkout, at which point anything that normally invokes the post-checkout hook will result in its execution, such as git checkout -b new-branch.

Impact

Arbitrary symlink creation into any existing directory the user can write to.

Disclosure

This vulnerability was found by AI (specifically, Claude Mythos) as part of Project Glasswing. This advisory was written and verified by a human.

Summary

A malicious tree can be constructed that will, when checked out with gitoxide, permit writing an attacker-controlled symlink into any existing directory the user has write access to.

Details

During checkout, all symlink index entries are deferred and created after regular files using a single shared gix_worktree::Stack. Internally, this uses a gix_fs::Stack.

gix_fs::Stack::make_relative_path_current() caches validated path prefixes: when the previously-processed leaf component exactly matches the leading component(s) of the next path, the leaf-to-directory transition at gix-fs/src/stack.rs:195-197 invokes only delegate.push_directory(), never delegate.push().

In gix_worktree::stack::delegate::StackDelegate, when the state member is State::CreateDirectoryAndAttributesStack, Attributes::push_directory() only loads attributes (from the ODB, in the clone case), and does not perform any other checks. The on-disk symlink_metadata() check and unlink-on-collision live in StackDelegate::push()'s invocation of create_leading_directory(), which is therefore bypassed for the cached prefix. The final symlink is created with plain std::os::unix::fs::symlink, which follows symlinks in parent directories.

Therefore, it's possible to provide a tree with duplicate symlink and directory entries that exploits this. If a tree is constructed with:

1. A 120000 (symlink) entry a that points to .git/hooks.
2. A 040000 (directory) entry a with a subtree that contains a symlink from post-checkout to ../../payload.
3. A 100755 (executable file) entry payload.

This is converted by gix_index::State::from_tree() into index entries ["a" (SYMLINK), "a/post-checkout" (SYMLINK)].

Then, during the delayed symlink phase:

1. a is created as a symlink to e.g. .git/hooks.
2. When processing a/post-checkout, the a prefix is reused from the just-processed leaf entry without re-running the intermediate-directory check, after which…
3. symlink(target, "<wt>/a/post-checkout") resolves through the just-created symlink to write .git/hooks/post-checkout.

Although this example uses .git/hooks for simplicity, there's no actual requirement to write within the repo checkout. This can be fairly easily chained into code execution by writing to something that is known to be executed — for example, by writing to .git/hooks/post-checkout if the attacker knows that a hook-aware Git implementation will be used later, or by writing to something like ~/.local/bin.

PoC

Attached is build-bad-repo.sh, which builds a repo with the aforementioned tree structure. Cloning it with gix will set up the malicious .git/hooks/post-checkout, at which point anything that normally invokes the post-checkout hook will result in its execution, such as git checkout -b new-branch.

Impact

Arbitrary symlink creation into any existing directory the user can write to.

Disclosure

This vulnerability was found by AI (specifically, Claude Mythos) as part of Project Glasswing. This advisory was written and verified by a human.

Summary

A malicious tree can be constructed that will, when checked out with gitoxide, permit writing an attacker-controlled symlink into any existing directory the user has write access to.

Details

During checkout, all symlink index entries are deferred and created after regular files using a single shared gix_worktree::Stack. Internally, this uses a gix_fs::Stack.

gix_fs::Stack::make_relative_path_current() caches validated path prefixes: when the previously-processed leaf component exactly matches the leading component(s) of the next path, the leaf-to-directory transition at gix-fs/src/stack.rs:195-197 invokes only delegate.push_directory(), never delegate.push().

In gix_worktree::stack::delegate::StackDelegate, when the state member is State::CreateDirectoryAndAttributesStack, Attributes::push_directory() only loads attributes (from the ODB, in the clone case), and does not perform any other checks. The on-disk symlink_metadata() check and unlink-on-collision live in StackDelegate::push()'s invocation of create_leading_directory(), which is therefore bypassed for the cached prefix. The final symlink is created with plain std::os::unix::fs::symlink, which follows symlinks in parent directories.

Therefore, it's possible to provide a tree with duplicate symlink and directory entries that exploits this. If a tree is constructed with:

1. A 120000 (symlink) entry a that points to .git/hooks.
2. A 040000 (directory) entry a with a subtree that contains a symlink from post-checkout to ../../payload.
3. A 100755 (executable file) entry payload.

This is converted by gix_index::State::from_tree() into index entries ["a" (SYMLINK), "a/post-checkout" (SYMLINK)].

Then, during the delayed symlink phase:

1. a is created as a symlink to e.g. .git/hooks.
2. When processing a/post-checkout, the a prefix is reused from the just-processed leaf entry without re-running the intermediate-directory check, after which…
3. symlink(target, "<wt>/a/post-checkout") resolves through the just-created symlink to write .git/hooks/post-checkout.

Although this example uses .git/hooks for simplicity, there's no actual requirement to write within the repo checkout. This can be fairly easily chained into code execution by writing to something that is known to be executed — for example, by writing to .git/hooks/post-checkout if the attacker knows that a hook-aware Git implementation will be used later, or by writing to something like ~/.local/bin.

PoC

Attached is build-bad-repo.sh, which builds a repo with the aforementioned tree structure. Cloning it with gix will set up the malicious .git/hooks/post-checkout, at which point anything that normally invokes the post-checkout hook will result in its execution, such as git checkout -b new-branch.

Impact

Arbitrary symlink creation into any existing directory the user can write to.

Disclosure

This vulnerability was found by AI (specifically, Claude Mythos) as part of Project Glasswing. This advisory was written and verified by a human.

Summary

A malicious tree can be constructed that will, when checked out with gitoxide, permit writing an attacker-controlled symlink into any existing directory the user has write access to.

Details

During checkout, all symlink index entries are deferred and created after regular files using a single shared gix_worktree::Stack. Internally, this uses a gix_fs::Stack.

gix_fs::Stack::make_relative_path_current() caches validated path prefixes: when the previously-processed leaf component exactly matches the leading component(s) of the next path, the leaf-to-directory transition at gix-fs/src/stack.rs:195-197 invokes only delegate.push_directory(), never delegate.push().

In gix_worktree::stack::delegate::StackDelegate, when the state member is State::CreateDirectoryAndAttributesStack, Attributes::push_directory() only loads attributes (from the ODB, in the clone case), and does not perform any other checks. The on-disk symlink_metadata() check and unlink-on-collision live in StackDelegate::push()'s invocation of create_leading_directory(), which is therefore bypassed for the cached prefix. The final symlink is created with plain std::os::unix::fs::symlink, which follows symlinks in parent directories.

Therefore, it's possible to provide a tree with duplicate symlink and directory entries that exploits this. If a tree is constructed with:

1. A 120000 (symlink) entry a that points to .git/hooks.
2. A 040000 (directory) entry a with a subtree that contains a symlink from post-checkout to ../../payload.
3. A 100755 (executable file) entry payload.

This is converted by gix_index::State::from_tree() into index entries ["a" (SYMLINK), "a/post-checkout" (SYMLINK)].

Then, during the delayed symlink phase:

1. a is created as a symlink to e.g. .git/hooks.
2. When processing a/post-checkout, the a prefix is reused from the just-processed leaf entry without re-running the intermediate-directory check, after which…
3. symlink(target, "<wt>/a/post-checkout") resolves through the just-created symlink to write .git/hooks/post-checkout.

Although this example uses .git/hooks for simplicity, there's no actual requirement to write within the repo checkout. This can be fairly easily chained into code execution by writing to something that is known to be executed — for example, by writing to .git/hooks/post-checkout if the attacker knows that a hook-aware Git implementation will be used later, or by writing to something like ~/.local/bin.

PoC

Attached is build-bad-repo.sh, which builds a repo with the aforementioned tree structure. Cloning it with gix will set up the malicious .git/hooks/post-checkout, at which point anything that normally invokes the post-checkout hook will result in its execution, such as git checkout -b new-branch.

Impact

Arbitrary symlink creation into any existing directory the user can write to.

Disclosure

This vulnerability was found by AI (specifically, Claude Mythos) as part of Project Glasswing. This advisory was written and verified by a human.

Summary

A malicious tree can be constructed that will, when checked out with gitoxide, permit writing an attacker-controlled symlink into any existing directory the user has write access to.

Details

During checkout, all symlink index entries are deferred and created after regular files using a single shared gix_worktree::Stack. Internally, this uses a gix_fs::Stack.

gix_fs::Stack::make_relative_path_current() caches validated path prefixes: when the previously-processed leaf component exactly matches the leading component(s) of the next path, the leaf-to-directory transition at gix-fs/src/stack.rs:195-197 invokes only delegate.push_directory(), never delegate.push().

In gix_worktree::stack::delegate::StackDelegate, when the state member is State::CreateDirectoryAndAttributesStack, Attributes::push_directory() only loads attributes (from the ODB, in the clone case), and does not perform any other checks. The on-disk symlink_metadata() check and unlink-on-collision live in StackDelegate::push()'s invocation of create_leading_directory(), which is therefore bypassed for the cached prefix. The final symlink is created with plain std::os::unix::fs::symlink, which follows symlinks in parent directories.

Therefore, it's possible to provide a tree with duplicate symlink and directory entries that exploits this. If a tree is constructed with:

1. A 120000 (symlink) entry a that points to .git/hooks.
2. A 040000 (directory) entry a with a subtree that contains a symlink from post-checkout to ../../payload.
3. A 100755 (executable file) entry payload.

This is converted by gix_index::State::from_tree() into index entries ["a" (SYMLINK), "a/post-checkout" (SYMLINK)].

Then, during the delayed symlink phase:

1. a is created as a symlink to e.g. .git/hooks.
2. When processing a/post-checkout, the a prefix is reused from the just-processed leaf entry without re-running the intermediate-directory check, after which…
3. symlink(target, "<wt>/a/post-checkout") resolves through the just-created symlink to write .git/hooks/post-checkout.

Although this example uses .git/hooks for simplicity, there's no actual requirement to write within the repo checkout. This can be fairly easily chained into code execution by writing to something that is known to be executed — for example, by writing to .git/hooks/post-checkout if the attacker knows that a hook-aware Git implementation will be used later, or by writing to something like ~/.local/bin.

PoC

Attached is build-bad-repo.sh, which builds a repo with the aforementioned tree structure. Cloning it with gix will set up the malicious .git/hooks/post-checkout, at which point anything that normally invokes the post-checkout hook will result in its execution, such as git checkout -b new-branch.

Impact

Arbitrary symlink creation into any existing directory the user can write to.

Disclosure

This vulnerability was found by AI (specifically, Claude Mythos) as part of Project Glasswing. This advisory was written and verified by a human.

Summary

A malicious tree can be constructed that will, when checked out with gitoxide, permit writing an attacker-controlled symlink into any existing directory the user has write access to.

Details

During checkout, all symlink index entries are deferred and created after regular files using a single shared gix_worktree::Stack. Internally, this uses a gix_fs::Stack.

gix_fs::Stack::make_relative_path_current() caches validated path prefixes: when the previously-processed leaf component exactly matches the leading component(s) of the next path, the leaf-to-directory transition at gix-fs/src/stack.rs:195-197 invokes only delegate.push_directory(), never delegate.push().

In gix_worktree::stack::delegate::StackDelegate, when the state member is State::CreateDirectoryAndAttributesStack, Attributes::push_directory() only loads attributes (from the ODB, in the clone case), and does not perform any other checks. The on-disk symlink_metadata() check and unlink-on-collision live in StackDelegate::push()'s invocation of create_leading_directory(), which is therefore bypassed for the cached prefix. The final symlink is created with plain std::os::unix::fs::symlink, which follows symlinks in parent directories.

Therefore, it's possible to provide a tree with duplicate symlink and directory entries that exploits this. If a tree is constructed with:

1. A 120000 (symlink) entry a that points to .git/hooks.
2. A 040000 (directory) entry a with a subtree that contains a symlink from post-checkout to ../../payload.
3. A 100755 (executable file) entry payload.

This is converted by gix_index::State::from_tree() into index entries ["a" (SYMLINK), "a/post-checkout" (SYMLINK)].

Then, during the delayed symlink phase:

1. a is created as a symlink to e.g. .git/hooks.
2. When processing a/post-checkout, the a prefix is reused from the just-processed leaf entry without re-running the intermediate-directory check, after which…
3. symlink(target, "<wt>/a/post-checkout") resolves through the just-created symlink to write .git/hooks/post-checkout.

Although this example uses .git/hooks for simplicity, there's no actual requirement to write within the repo checkout. This can be fairly easily chained into code execution by writing to something that is known to be executed — for example, by writing to .git/hooks/post-checkout if the attacker knows that a hook-aware Git implementation will be used later, or by writing to something like ~/.local/bin.

PoC

Attached is build-bad-repo.sh, which builds a repo with the aforementioned tree structure. Cloning it with gix will set up the malicious .git/hooks/post-checkout, at which point anything that normally invokes the post-checkout hook will result in its execution, such as git checkout -b new-branch.

Impact

Arbitrary symlink creation into any existing directory the user can write to.

Disclosure

This vulnerability was found by AI (specifically, Claude Mythos) as part of Project Glasswing. This advisory was written and verified by a human.

Summary

A malicious tree can be constructed that will, when checked out with gitoxide, permit writing an attacker-controlled symlink into any existing directory the user has write access to.

Details

During checkout, all symlink index entries are deferred and created after regular files using a single shared gix_worktree::Stack. Internally, this uses a gix_fs::Stack.

gix_fs::Stack::make_relative_path_current() caches validated path prefixes: when the previously-processed leaf component exactly matches the leading component(s) of the next path, the leaf-to-directory transition at gix-fs/src/stack.rs:195-197 invokes only delegate.push_directory(), never delegate.push().

In gix_worktree::stack::delegate::StackDelegate, when the state member is State::CreateDirectoryAndAttributesStack, Attributes::push_directory() only loads attributes (from the ODB, in the clone case), and does not perform any other checks. The on-disk symlink_metadata() check and unlink-on-collision live in StackDelegate::push()'s invocation of create_leading_directory(), which is therefore bypassed for the cached prefix. The final symlink is created with plain std::os::unix::fs::symlink, which follows symlinks in parent directories.

Therefore, it's possible to provide a tree with duplicate symlink and directory entries that exploits this. If a tree is constructed with:

1. A 120000 (symlink) entry a that points to .git/hooks.
2. A 040000 (directory) entry a with a subtree that contains a symlink from post-checkout to ../../payload.
3. A 100755 (executable file) entry payload.

This is converted by gix_index::State::from_tree() into index entries ["a" (SYMLINK), "a/post-checkout" (SYMLINK)].

Then, during the delayed symlink phase:

1. a is created as a symlink to e.g. .git/hooks.
2. When processing a/post-checkout, the a prefix is reused from the just-processed leaf entry without re-running the intermediate-directory check, after which…
3. symlink(target, "<wt>/a/post-checkout") resolves through the just-created symlink to write .git/hooks/post-checkout.

Although this example uses .git/hooks for simplicity, there's no actual requirement to write within the repo checkout. This can be fairly easily chained into code execution by writing to something that is known to be executed — for example, by writing to .git/hooks/post-checkout if the attacker knows that a hook-aware Git implementation will be used later, or by writing to something like ~/.local/bin.

PoC

Attached is build-bad-repo.sh, which builds a repo with the aforementioned tree structure. Cloning it with gix will set up the malicious .git/hooks/post-checkout, at which point anything that normally invokes the post-checkout hook will result in its execution, such as git checkout -b new-branch.

Impact

Arbitrary symlink creation into any existing directory the user can write to.

Disclosure

This vulnerability was found by AI (specifically, Claude Mythos) as part of Project Glasswing. This advisory was written and verified by a human.

Summary

A malicious tree can be constructed that will, when checked out with gitoxide, permit writing an attacker-controlled symlink into any existing directory the user has write access to.

Details

During checkout, all symlink index entries are deferred and created after regular files using a single shared gix_worktree::Stack. Internally, this uses a gix_fs::Stack.

gix_fs::Stack::make_relative_path_current() caches validated path prefixes: when the previously-processed leaf component exactly matches the leading component(s) of the next path, the leaf-to-directory transition at gix-fs/src/stack.rs:195-197 invokes only delegate.push_directory(), never delegate.push().

In gix_worktree::stack::delegate::StackDelegate, when the state member is State::CreateDirectoryAndAttributesStack, Attributes::push_directory() only loads attributes (from the ODB, in the clone case), and does not perform any other checks. The on-disk symlink_metadata() check and unlink-on-collision live in StackDelegate::push()'s invocation of create_leading_directory(), which is therefore bypassed for the cached prefix. The final symlink is created with plain std::os::unix::fs::symlink, which follows symlinks in parent directories.

Therefore, it's possible to provide a tree with duplicate symlink and directory entries that exploits this. If a tree is constructed with:

1. A 120000 (symlink) entry a that points to .git/hooks.
2. A 040000 (directory) entry a with a subtree that contains a symlink from post-checkout to ../../payload.
3. A 100755 (executable file) entry payload.

This is converted by gix_index::State::from_tree() into index entries ["a" (SYMLINK), "a/post-checkout" (SYMLINK)].

Then, during the delayed symlink phase:

1. a is created as a symlink to e.g. .git/hooks.
2. When processing a/post-checkout, the a prefix is reused from the just-processed leaf entry without re-running the intermediate-directory check, after which…
3. symlink(target, "<wt>/a/post-checkout") resolves through the just-created symlink to write .git/hooks/post-checkout.

Although this example uses .git/hooks for simplicity, there's no actual requirement to write within the repo checkout. This can be fairly easily chained into code execution by writing to something that is known to be executed — for example, by writing to .git/hooks/post-checkout if the attacker knows that a hook-aware Git implementation will be used later, or by writing to something like ~/.local/bin.

PoC

Attached is build-bad-repo.sh, which builds a repo with the aforementioned tree structure. Cloning it with gix will set up the malicious .git/hooks/post-checkout, at which point anything that normally invokes the post-checkout hook will result in its execution, such as git checkout -b new-branch.

Impact

Arbitrary symlink creation into any existing directory the user can write to.

Disclosure

This vulnerability was found by AI (specifically, Claude Mythos) as part of Project Glasswing. This advisory was written and verified by a human.

Summary

A malicious tree can be constructed that will, when checked out with gitoxide, permit writing an attacker-controlled symlink into any existing directory the user has write access to.

Details

During checkout, all symlink index entries are deferred and created after regular files using a single shared gix_worktree::Stack. Internally, this uses a gix_fs::Stack.

gix_fs::Stack::make_relative_path_current() caches validated path prefixes: when the previously-processed leaf component exactly matches the leading component(s) of the next path, the leaf-to-directory transition at gix-fs/src/stack.rs:195-197 invokes only delegate.push_directory(), never delegate.push().

In gix_worktree::stack::delegate::StackDelegate, when the state member is State::CreateDirectoryAndAttributesStack, Attributes::push_directory() only loads attributes (from the ODB, in the clone case), and does not perform any other checks. The on-disk symlink_metadata() check and unlink-on-collision live in StackDelegate::push()'s invocation of create_leading_directory(), which is therefore bypassed for the cached prefix. The final symlink is created with plain std::os::unix::fs::symlink, which follows symlinks in parent directories.

Therefore, it's possible to provide a tree with duplicate symlink and directory entries that exploits this. If a tree is constructed with:

1. A 120000 (symlink) entry a that points to .git/hooks.
2. A 040000 (directory) entry a with a subtree that contains a symlink from post-checkout to ../../payload.
3. A 100755 (executable file) entry payload.

This is converted by gix_index::State::from_tree() into index entries ["a" (SYMLINK), "a/post-checkout" (SYMLINK)].

Then, during the delayed symlink phase:

1. a is created as a symlink to e.g. .git/hooks.
2. When processing a/post-checkout, the a prefix is reused from the just-processed leaf entry without re-running the intermediate-directory check, after which…
3. symlink(target, "<wt>/a/post-checkout") resolves through the just-created symlink to write .git/hooks/post-checkout.

Although this example uses .git/hooks for simplicity, there's no actual requirement to write within the repo checkout. This can be fairly easily chained into code execution by writing to something that is known to be executed — for example, by writing to .git/hooks/post-checkout if the attacker knows that a hook-aware Git implementation will be used later, or by writing to something like ~/.local/bin.

PoC

Attached is build-bad-repo.sh, which builds a repo with the aforementioned tree structure. Cloning it with gix will set up the malicious .git/hooks/post-checkout, at which point anything that normally invokes the post-checkout hook will result in its execution, such as git checkout -b new-branch.

Impact

Arbitrary symlink creation into any existing directory the user can write to.

Disclosure

This vulnerability was found by AI (specifically, Claude Mythos) as part of Project Glasswing. This advisory was written and verified by a human.

Summary

During checkout, gitoxide does not verify that paths point to locations in the working tree. A specially crafted repository can, when cloned, place new files anywhere writable by the application.

Details

Although gix-worktree-state checks for collisions with existing files, it does not itself check if a path is really in the working tree when performing a checkout, nor do the path checks in gix-fs and gix-worktree prevent this. Cloning an untrusted repository containing specially crafted tree or blob names will create new files outside the repository, or inside the repository or a submodule's .git directory. The simplest cases are:

• A tree named .. to traverse upward. This facilitates arbitrary code execution because files can be placed in one or more locations where they are likely to be executed soon.
• A tree named .git to enter a .git directory. This facilitates arbitrary code execution because hooks can be installed.

A number of alternatives that achieve the same effect are also possible, some of which correspond to specific vulnerabilities that have affected Git in the past:

• A tree or blob whose name contains one or more /, to traverse upward or downward. For example, even without containing any tree named .. or .git, a repository can represent a file named ../outside or .git/hooks/pre-commit. This is distinct from the more intuitive case a repository containing trees that represent those paths.
• In Windows, a tree or blob whose name contains one or more \, to traverse upward or downward. (Unlike /, these are valid on other systems.) See GHSA-xjx4-8694-q2fq.
• On a case-insensitive filesystem (such as NTFS, APFS, or HFS+), a tree named as a case variant of .git.
• On HFS+, a tree named like .git or a case variant, with characters added that HFS+ ignores in collation. See https://github.com/git/git/commit/6162a1d323d24fd8cbbb1a6145a91fb849b2568f.
• On NTFS, a tree equivalent to .git (or a case variant) by the use of NTFS stream notation, such as .git::$INDEX_ALLOCATION. See GHSA-5wph-8frv-58vj.
• On an NTFS volume with 8.3 aliasing enabled, a tree named as git~1 (or a case variant). See GHSA-589j-mmg9-733v.

When a checkout creates some files outside the repository directory but fails to complete, the repository directory is usually removed, but the outside files remain.

PoC

For simplicity, these examples stage a stand-in file with a valid name, modify the index, and commit. The instructions assume sed supports -i, which is the case on most systems. If using Windows, a Git Bash shell should be used.

Example: Downward traversal to install hooks

1. Create a new repository with git init dangerous-repo-installs-hook and cd into the directory.
2. Create the stand-in called .git@hooks@pre-commit, with the contents:

   #!/bin/sh
   printf 'Vulnerable!\n'
   date >vulnerable
   

3. Stage the stand-in: git add --chmod=+x .git@hooks@pre-commit
4. Edit the index: env LC_ALL=C sed -i.orig 's|\.git@hooks@pre-commit|.git/hooks/pre-commit|' .git/index
5. Commit: git commit -m 'Initial commit'
6. Optionally, push to a private remote.

Then, on another or the same machine:

1. Clone the repository with a gix clone … command.
2. Enter the newly created directory.
3. Optionally run ls -l .git/hooks to observe that the pre-commit hook is already present.
4. Make a new file and commit it with git. This causes the payload surreptitiously installed as a pre-commit hook to run, printing the message Vulnerable! and creating a file in the current directory containing the current date and time.

Note that the effect is not limited to modifying the current directory. The payload could be written to perform any action that the user who runs git commit is capable of.

Example: Upward traversal to create a file above the working tree

1. Create a new repository with git init dangerous-repo-reaches-up, and cd into the directory.
2. Create the stand-in: echo 'A file outside the working tree, somehow.' >..@outside
3. Stage the stand-in: git add ..@outside
4. Edit the index: env LC_ALL=C sed -i.orig 's|\.\.@outside|../outside|' .git/index
5. Commit: git commit -m 'Initial commit'
6. Optionally, push to a private remote.

Then, as above, on the same or another machine, clone the repository with a gix clone … command. Observe that a file named outside is present alongside (not inside) the cloned directory.

Impact

Any use of gix or another application that makes use of gix-worktree-state, or otherwise relies on gix-fs and gix-worktree for validation, is affected, if used to clone untrusted repositories. The above description focuses on code execution, as that leads to a complete loss of confidentiality, integrity, and availability, but creating files outside a working tree without attempting to execute code can directly impact integrity as well.

In use cases where no untrusted repository is ever cloned, this vulnerability has no impact. Furthermore, the impact of this vulnerability may be lower when gix is used to clone a repository for CI/CD purposes, even if untrusted, since in such uses the environment is usually isolated and arbitrary code is usually run deliberately from the repository with necessary safeguards in place.

Summary

A malicious tree can be constructed that will, when checked out with gitoxide, permit writing an attacker-controlled symlink into any existing directory the user has write access to.

Details

During checkout, all symlink index entries are deferred and created after regular files using a single shared gix_worktree::Stack. Internally, this uses a gix_fs::Stack.

gix_fs::Stack::make_relative_path_current() caches validated path prefixes: when the previously-processed leaf component exactly matches the leading component(s) of the next path, the leaf-to-directory transition at gix-fs/src/stack.rs:195-197 invokes only delegate.push_directory(), never delegate.push().

In gix_worktree::stack::delegate::StackDelegate, when the state member is State::CreateDirectoryAndAttributesStack, Attributes::push_directory() only loads attributes (from the ODB, in the clone case), and does not perform any other checks. The on-disk symlink_metadata() check and unlink-on-collision live in StackDelegate::push()'s invocation of create_leading_directory(), which is therefore bypassed for the cached prefix. The final symlink is created with plain std::os::unix::fs::symlink, which follows symlinks in parent directories.

Therefore, it's possible to provide a tree with duplicate symlink and directory entries that exploits this. If a tree is constructed with:

1. A 120000 (symlink) entry a that points to .git/hooks.
2. A 040000 (directory) entry a with a subtree that contains a symlink from post-checkout to ../../payload.
3. A 100755 (executable file) entry payload.

This is converted by gix_index::State::from_tree() into index entries ["a" (SYMLINK), "a/post-checkout" (SYMLINK)].

Then, during the delayed symlink phase:

1. a is created as a symlink to e.g. .git/hooks.
2. When processing a/post-checkout, the a prefix is reused from the just-processed leaf entry without re-running the intermediate-directory check, after which…
3. symlink(target, "<wt>/a/post-checkout") resolves through the just-created symlink to write .git/hooks/post-checkout.

Although this example uses .git/hooks for simplicity, there's no actual requirement to write within the repo checkout. This can be fairly easily chained into code execution by writing to something that is known to be executed — for example, by writing to .git/hooks/post-checkout if the attacker knows that a hook-aware Git implementation will be used later, or by writing to something like ~/.local/bin.

PoC

Attached is build-bad-repo.sh, which builds a repo with the aforementioned tree structure. Cloning it with gix will set up the malicious .git/hooks/post-checkout, at which point anything that normally invokes the post-checkout hook will result in its execution, such as git checkout -b new-branch.

Impact

Arbitrary symlink creation into any existing directory the user can write to.

Disclosure

This vulnerability was found by AI (specifically, Claude Mythos) as part of Project Glasswing. This advisory was written and verified by a human.

Summary

During checkout, gitoxide does not verify that paths point to locations in the working tree. A specially crafted repository can, when cloned, place new files anywhere writable by the application.

Details

Although gix-worktree-state checks for collisions with existing files, it does not itself check if a path is really in the working tree when performing a checkout, nor do the path checks in gix-fs and gix-worktree prevent this. Cloning an untrusted repository containing specially crafted tree or blob names will create new files outside the repository, or inside the repository or a submodule's .git directory. The simplest cases are:

• A tree named .. to traverse upward. This facilitates arbitrary code execution because files can be placed in one or more locations where they are likely to be executed soon.
• A tree named .git to enter a .git directory. This facilitates arbitrary code execution because hooks can be installed.

A number of alternatives that achieve the same effect are also possible, some of which correspond to specific vulnerabilities that have affected Git in the past:

• A tree or blob whose name contains one or more /, to traverse upward or downward. For example, even without containing any tree named .. or .git, a repository can represent a file named ../outside or .git/hooks/pre-commit. This is distinct from the more intuitive case a repository containing trees that represent those paths.
• In Windows, a tree or blob whose name contains one or more \, to traverse upward or downward. (Unlike /, these are valid on other systems.) See GHSA-xjx4-8694-q2fq.
• On a case-insensitive filesystem (such as NTFS, APFS, or HFS+), a tree named as a case variant of .git.
• On HFS+, a tree named like .git or a case variant, with characters added that HFS+ ignores in collation. See https://github.com/git/git/commit/6162a1d323d24fd8cbbb1a6145a91fb849b2568f.
• On NTFS, a tree equivalent to .git (or a case variant) by the use of NTFS stream notation, such as .git::$INDEX_ALLOCATION. See GHSA-5wph-8frv-58vj.
• On an NTFS volume with 8.3 aliasing enabled, a tree named as git~1 (or a case variant). See GHSA-589j-mmg9-733v.

When a checkout creates some files outside the repository directory but fails to complete, the repository directory is usually removed, but the outside files remain.

PoC

For simplicity, these examples stage a stand-in file with a valid name, modify the index, and commit. The instructions assume sed supports -i, which is the case on most systems. If using Windows, a Git Bash shell should be used.

Example: Downward traversal to install hooks

1. Create a new repository with git init dangerous-repo-installs-hook and cd into the directory.
2. Create the stand-in called .git@hooks@pre-commit, with the contents:

   #!/bin/sh
   printf 'Vulnerable!\n'
   date >vulnerable
   

3. Stage the stand-in: git add --chmod=+x .git@hooks@pre-commit
4. Edit the index: env LC_ALL=C sed -i.orig 's|\.git@hooks@pre-commit|.git/hooks/pre-commit|' .git/index
5. Commit: git commit -m 'Initial commit'
6. Optionally, push to a private remote.

Then, on another or the same machine:

1. Clone the repository with a gix clone … command.
2. Enter the newly created directory.
3. Optionally run ls -l .git/hooks to observe that the pre-commit hook is already present.
4. Make a new file and commit it with git. This causes the payload surreptitiously installed as a pre-commit hook to run, printing the message Vulnerable! and creating a file in the current directory containing the current date and time.

Note that the effect is not limited to modifying the current directory. The payload could be written to perform any action that the user who runs git commit is capable of.

Example: Upward traversal to create a file above the working tree

1. Create a new repository with git init dangerous-repo-reaches-up, and cd into the directory.
2. Create the stand-in: echo 'A file outside the working tree, somehow.' >..@outside
3. Stage the stand-in: git add ..@outside
4. Edit the index: env LC_ALL=C sed -i.orig 's|\.\.@outside|../outside|' .git/index
5. Commit: git commit -m 'Initial commit'
6. Optionally, push to a private remote.

Then, as above, on the same or another machine, clone the repository with a gix clone … command. Observe that a file named outside is present alongside (not inside) the cloned directory.

Impact

Any use of gix or another application that makes use of gix-worktree-state, or otherwise relies on gix-fs and gix-worktree for validation, is affected, if used to clone untrusted repositories. The above description focuses on code execution, as that leads to a complete loss of confidentiality, integrity, and availability, but creating files outside a working tree without attempting to execute code can directly impact integrity as well.

In use cases where no untrusted repository is ever cloned, this vulnerability has no impact. Furthermore, the impact of this vulnerability may be lower when gix is used to clone a repository for CI/CD purposes, even if untrusted, since in such uses the environment is usually isolated and arbitrary code is usually run deliberately from the repository with necessary safeguards in place.

Summary

A malicious tree can be constructed that will, when checked out with gitoxide, permit writing an attacker-controlled symlink into any existing directory the user has write access to.

Details

During checkout, all symlink index entries are deferred and created after regular files using a single shared gix_worktree::Stack. Internally, this uses a gix_fs::Stack.

gix_fs::Stack::make_relative_path_current() caches validated path prefixes: when the previously-processed leaf component exactly matches the leading component(s) of the next path, the leaf-to-directory transition at gix-fs/src/stack.rs:195-197 invokes only delegate.push_directory(), never delegate.push().

In gix_worktree::stack::delegate::StackDelegate, when the state member is State::CreateDirectoryAndAttributesStack, Attributes::push_directory() only loads attributes (from the ODB, in the clone case), and does not perform any other checks. The on-disk symlink_metadata() check and unlink-on-collision live in StackDelegate::push()'s invocation of create_leading_directory(), which is therefore bypassed for the cached prefix. The final symlink is created with plain std::os::unix::fs::symlink, which follows symlinks in parent directories.

Therefore, it's possible to provide a tree with duplicate symlink and directory entries that exploits this. If a tree is constructed with:

1. A 120000 (symlink) entry a that points to .git/hooks.
2. A 040000 (directory) entry a with a subtree that contains a symlink from post-checkout to ../../payload.
3. A 100755 (executable file) entry payload.

This is converted by gix_index::State::from_tree() into index entries ["a" (SYMLINK), "a/post-checkout" (SYMLINK)].

Then, during the delayed symlink phase:

1. a is created as a symlink to e.g. .git/hooks.
2. When processing a/post-checkout, the a prefix is reused from the just-processed leaf entry without re-running the intermediate-directory check, after which…
3. symlink(target, "<wt>/a/post-checkout") resolves through the just-created symlink to write .git/hooks/post-checkout.

Although this example uses .git/hooks for simplicity, there's no actual requirement to write within the repo checkout. This can be fairly easily chained into code execution by writing to something that is known to be executed — for example, by writing to .git/hooks/post-checkout if the attacker knows that a hook-aware Git implementation will be used later, or by writing to something like ~/.local/bin.

PoC

Attached is build-bad-repo.sh, which builds a repo with the aforementioned tree structure. Cloning it with gix will set up the malicious .git/hooks/post-checkout, at which point anything that normally invokes the post-checkout hook will result in its execution, such as git checkout -b new-branch.

Impact

Arbitrary symlink creation into any existing directory the user can write to.

Disclosure

This vulnerability was found by AI (specifically, Claude Mythos) as part of Project Glasswing. This advisory was written and verified by a human.

Summary

During checkout, gitoxide does not verify that paths point to locations in the working tree. A specially crafted repository can, when cloned, place new files anywhere writable by the application.

Details

Although gix-worktree-state checks for collisions with existing files, it does not itself check if a path is really in the working tree when performing a checkout, nor do the path checks in gix-fs and gix-worktree prevent this. Cloning an untrusted repository containing specially crafted tree or blob names will create new files outside the repository, or inside the repository or a submodule's .git directory. The simplest cases are:

• A tree named .. to traverse upward. This facilitates arbitrary code execution because files can be placed in one or more locations where they are likely to be executed soon.
• A tree named .git to enter a .git directory. This facilitates arbitrary code execution because hooks can be installed.

A number of alternatives that achieve the same effect are also possible, some of which correspond to specific vulnerabilities that have affected Git in the past:

• A tree or blob whose name contains one or more /, to traverse upward or downward. For example, even without containing any tree named .. or .git, a repository can represent a file named ../outside or .git/hooks/pre-commit. This is distinct from the more intuitive case a repository containing trees that represent those paths.
• In Windows, a tree or blob whose name contains one or more \, to traverse upward or downward. (Unlike /, these are valid on other systems.) See GHSA-xjx4-8694-q2fq.
• On a case-insensitive filesystem (such as NTFS, APFS, or HFS+), a tree named as a case variant of .git.
• On HFS+, a tree named like .git or a case variant, with characters added that HFS+ ignores in collation. See https://github.com/git/git/commit/6162a1d323d24fd8cbbb1a6145a91fb849b2568f.
• On NTFS, a tree equivalent to .git (or a case variant) by the use of NTFS stream notation, such as .git::$INDEX_ALLOCATION. See GHSA-5wph-8frv-58vj.
• On an NTFS volume with 8.3 aliasing enabled, a tree named as git~1 (or a case variant). See GHSA-589j-mmg9-733v.

When a checkout creates some files outside the repository directory but fails to complete, the repository directory is usually removed, but the outside files remain.

PoC

For simplicity, these examples stage a stand-in file with a valid name, modify the index, and commit. The instructions assume sed supports -i, which is the case on most systems. If using Windows, a Git Bash shell should be used.

Example: Downward traversal to install hooks

1. Create a new repository with git init dangerous-repo-installs-hook and cd into the directory.
2. Create the stand-in called .git@hooks@pre-commit, with the contents:

   #!/bin/sh
   printf 'Vulnerable!\n'
   date >vulnerable
   

3. Stage the stand-in: git add --chmod=+x .git@hooks@pre-commit
4. Edit the index: env LC_ALL=C sed -i.orig 's|\.git@hooks@pre-commit|.git/hooks/pre-commit|' .git/index
5. Commit: git commit -m 'Initial commit'
6. Optionally, push to a private remote.

Then, on another or the same machine:

1. Clone the repository with a gix clone … command.
2. Enter the newly created directory.
3. Optionally run ls -l .git/hooks to observe that the pre-commit hook is already present.
4. Make a new file and commit it with git. This causes the payload surreptitiously installed as a pre-commit hook to run, printing the message Vulnerable! and creating a file in the current directory containing the current date and time.

Note that the effect is not limited to modifying the current directory. The payload could be written to perform any action that the user who runs git commit is capable of.

Example: Upward traversal to create a file above the working tree

1. Create a new repository with git init dangerous-repo-reaches-up, and cd into the directory.
2. Create the stand-in: echo 'A file outside the working tree, somehow.' >..@outside
3. Stage the stand-in: git add ..@outside
4. Edit the index: env LC_ALL=C sed -i.orig 's|\.\.@outside|../outside|' .git/index
5. Commit: git commit -m 'Initial commit'
6. Optionally, push to a private remote.

Then, as above, on the same or another machine, clone the repository with a gix clone … command. Observe that a file named outside is present alongside (not inside) the cloned directory.

Impact

Any use of gix or another application that makes use of gix-worktree-state, or otherwise relies on gix-fs and gix-worktree for validation, is affected, if used to clone untrusted repositories. The above description focuses on code execution, as that leads to a complete loss of confidentiality, integrity, and availability, but creating files outside a working tree without attempting to execute code can directly impact integrity as well.

In use cases where no untrusted repository is ever cloned, this vulnerability has no impact. Furthermore, the impact of this vulnerability may be lower when gix is used to clone a repository for CI/CD purposes, even if untrusted, since in such uses the environment is usually isolated and arbitrary code is usually run deliberately from the repository with necessary safeguards in place.

Summary

A malicious tree can be constructed that will, when checked out with gitoxide, permit writing an attacker-controlled symlink into any existing directory the user has write access to.

Details

During checkout, all symlink index entries are deferred and created after regular files using a single shared gix_worktree::Stack. Internally, this uses a gix_fs::Stack.

gix_fs::Stack::make_relative_path_current() caches validated path prefixes: when the previously-processed leaf component exactly matches the leading component(s) of the next path, the leaf-to-directory transition at gix-fs/src/stack.rs:195-197 invokes only delegate.push_directory(), never delegate.push().

In gix_worktree::stack::delegate::StackDelegate, when the state member is State::CreateDirectoryAndAttributesStack, Attributes::push_directory() only loads attributes (from the ODB, in the clone case), and does not perform any other checks. The on-disk symlink_metadata() check and unlink-on-collision live in StackDelegate::push()'s invocation of create_leading_directory(), which is therefore bypassed for the cached prefix. The final symlink is created with plain std::os::unix::fs::symlink, which follows symlinks in parent directories.

Therefore, it's possible to provide a tree with duplicate symlink and directory entries that exploits this. If a tree is constructed with:

1. A 120000 (symlink) entry a that points to .git/hooks.
2. A 040000 (directory) entry a with a subtree that contains a symlink from post-checkout to ../../payload.
3. A 100755 (executable file) entry payload.

This is converted by gix_index::State::from_tree() into index entries ["a" (SYMLINK), "a/post-checkout" (SYMLINK)].

Then, during the delayed symlink phase:

1. a is created as a symlink to e.g. .git/hooks.
2. When processing a/post-checkout, the a prefix is reused from the just-processed leaf entry without re-running the intermediate-directory check, after which…
3. symlink(target, "<wt>/a/post-checkout") resolves through the just-created symlink to write .git/hooks/post-checkout.

Although this example uses .git/hooks for simplicity, there's no actual requirement to write within the repo checkout. This can be fairly easily chained into code execution by writing to something that is known to be executed — for example, by writing to .git/hooks/post-checkout if the attacker knows that a hook-aware Git implementation will be used later, or by writing to something like ~/.local/bin.

PoC

Attached is build-bad-repo.sh, which builds a repo with the aforementioned tree structure. Cloning it with gix will set up the malicious .git/hooks/post-checkout, at which point anything that normally invokes the post-checkout hook will result in its execution, such as git checkout -b new-branch.

Impact

Arbitrary symlink creation into any existing directory the user can write to.

Disclosure

This vulnerability was found by AI (specifically, Claude Mythos) as part of Project Glasswing. This advisory was written and verified by a human.

Summary

During checkout, gitoxide does not verify that paths point to locations in the working tree. A specially crafted repository can, when cloned, place new files anywhere writable by the application.

Details

Although gix-worktree-state checks for collisions with existing files, it does not itself check if a path is really in the working tree when performing a checkout, nor do the path checks in gix-fs and gix-worktree prevent this. Cloning an untrusted repository containing specially crafted tree or blob names will create new files outside the repository, or inside the repository or a submodule's .git directory. The simplest cases are:

• A tree named .. to traverse upward. This facilitates arbitrary code execution because files can be placed in one or more locations where they are likely to be executed soon.
• A tree named .git to enter a .git directory. This facilitates arbitrary code execution because hooks can be installed.

A number of alternatives that achieve the same effect are also possible, some of which correspond to specific vulnerabilities that have affected Git in the past:

• A tree or blob whose name contains one or more /, to traverse upward or downward. For example, even without containing any tree named .. or .git, a repository can represent a file named ../outside or .git/hooks/pre-commit. This is distinct from the more intuitive case a repository containing trees that represent those paths.
• In Windows, a tree or blob whose name contains one or more \, to traverse upward or downward. (Unlike /, these are valid on other systems.) See GHSA-xjx4-8694-q2fq.
• On a case-insensitive filesystem (such as NTFS, APFS, or HFS+), a tree named as a case variant of .git.
• On HFS+, a tree named like .git or a case variant, with characters added that HFS+ ignores in collation. See https://github.com/git/git/commit/6162a1d323d24fd8cbbb1a6145a91fb849b2568f.
• On NTFS, a tree equivalent to .git (or a case variant) by the use of NTFS stream notation, such as .git::$INDEX_ALLOCATION. See GHSA-5wph-8frv-58vj.
• On an NTFS volume with 8.3 aliasing enabled, a tree named as git~1 (or a case variant). See GHSA-589j-mmg9-733v.

When a checkout creates some files outside the repository directory but fails to complete, the repository directory is usually removed, but the outside files remain.

PoC

For simplicity, these examples stage a stand-in file with a valid name, modify the index, and commit. The instructions assume sed supports -i, which is the case on most systems. If using Windows, a Git Bash shell should be used.

Example: Downward traversal to install hooks

1. Create a new repository with git init dangerous-repo-installs-hook and cd into the directory.
2. Create the stand-in called .git@hooks@pre-commit, with the contents:

   #!/bin/sh
   printf 'Vulnerable!\n'
   date >vulnerable
   

3. Stage the stand-in: git add --chmod=+x .git@hooks@pre-commit
4. Edit the index: env LC_ALL=C sed -i.orig 's|\.git@hooks@pre-commit|.git/hooks/pre-commit|' .git/index
5. Commit: git commit -m 'Initial commit'
6. Optionally, push to a private remote.

Then, on another or the same machine:

1. Clone the repository with a gix clone … command.
2. Enter the newly created directory.
3. Optionally run ls -l .git/hooks to observe that the pre-commit hook is already present.
4. Make a new file and commit it with git. This causes the payload surreptitiously installed as a pre-commit hook to run, printing the message Vulnerable! and creating a file in the current directory containing the current date and time.

Note that the effect is not limited to modifying the current directory. The payload could be written to perform any action that the user who runs git commit is capable of.

Example: Upward traversal to create a file above the working tree

1. Create a new repository with git init dangerous-repo-reaches-up, and cd into the directory.
2. Create the stand-in: echo 'A file outside the working tree, somehow.' >..@outside
3. Stage the stand-in: git add ..@outside
4. Edit the index: env LC_ALL=C sed -i.orig 's|\.\.@outside|../outside|' .git/index
5. Commit: git commit -m 'Initial commit'
6. Optionally, push to a private remote.

Then, as above, on the same or another machine, clone the repository with a gix clone … command. Observe that a file named outside is present alongside (not inside) the cloned directory.

Impact

Any use of gix or another application that makes use of gix-worktree-state, or otherwise relies on gix-fs and gix-worktree for validation, is affected, if used to clone untrusted repositories. The above description focuses on code execution, as that leads to a complete loss of confidentiality, integrity, and availability, but creating files outside a working tree without attempting to execute code can directly impact integrity as well.

In use cases where no untrusted repository is ever cloned, this vulnerability has no impact. Furthermore, the impact of this vulnerability may be lower when gix is used to clone a repository for CI/CD purposes, even if untrusted, since in such uses the environment is usually isolated and arbitrary code is usually run deliberately from the repository with necessary safeguards in place.

Summary

A malicious tree can be constructed that will, when checked out with gitoxide, permit writing an attacker-controlled symlink into any existing directory the user has write access to.

Details

During checkout, all symlink index entries are deferred and created after regular files using a single shared gix_worktree::Stack. Internally, this uses a gix_fs::Stack.

gix_fs::Stack::make_relative_path_current() caches validated path prefixes: when the previously-processed leaf component exactly matches the leading component(s) of the next path, the leaf-to-directory transition at gix-fs/src/stack.rs:195-197 invokes only delegate.push_directory(), never delegate.push().

In gix_worktree::stack::delegate::StackDelegate, when the state member is State::CreateDirectoryAndAttributesStack, Attributes::push_directory() only loads attributes (from the ODB, in the clone case), and does not perform any other checks. The on-disk symlink_metadata() check and unlink-on-collision live in StackDelegate::push()'s invocation of create_leading_directory(), which is therefore bypassed for the cached prefix. The final symlink is created with plain std::os::unix::fs::symlink, which follows symlinks in parent directories.

Therefore, it's possible to provide a tree with duplicate symlink and directory entries that exploits this. If a tree is constructed with:

1. A 120000 (symlink) entry a that points to .git/hooks.
2. A 040000 (directory) entry a with a subtree that contains a symlink from post-checkout to ../../payload.
3. A 100755 (executable file) entry payload.

This is converted by gix_index::State::from_tree() into index entries ["a" (SYMLINK), "a/post-checkout" (SYMLINK)].

Then, during the delayed symlink phase:

1. a is created as a symlink to e.g. .git/hooks.
2. When processing a/post-checkout, the a prefix is reused from the just-processed leaf entry without re-running the intermediate-directory check, after which…
3. symlink(target, "<wt>/a/post-checkout") resolves through the just-created symlink to write .git/hooks/post-checkout.

Although this example uses .git/hooks for simplicity, there's no actual requirement to write within the repo checkout. This can be fairly easily chained into code execution by writing to something that is known to be executed — for example, by writing to .git/hooks/post-checkout if the attacker knows that a hook-aware Git implementation will be used later, or by writing to something like ~/.local/bin.

PoC

Attached is build-bad-repo.sh, which builds a repo with the aforementioned tree structure. Cloning it with gix will set up the malicious .git/hooks/post-checkout, at which point anything that normally invokes the post-checkout hook will result in its execution, such as git checkout -b new-branch.

Impact

Arbitrary symlink creation into any existing directory the user can write to.

Disclosure

This vulnerability was found by AI (specifically, Claude Mythos) as part of Project Glasswing. This advisory was written and verified by a human.

Summary

During checkout, gitoxide does not verify that paths point to locations in the working tree. A specially crafted repository can, when cloned, place new files anywhere writable by the application.

Details

Although gix-worktree-state checks for collisions with existing files, it does not itself check if a path is really in the working tree when performing a checkout, nor do the path checks in gix-fs and gix-worktree prevent this. Cloning an untrusted repository containing specially crafted tree or blob names will create new files outside the repository, or inside the repository or a submodule's .git directory. The simplest cases are:

• A tree named .. to traverse upward. This facilitates arbitrary code execution because files can be placed in one or more locations where they are likely to be executed soon.
• A tree named .git to enter a .git directory. This facilitates arbitrary code execution because hooks can be installed.

A number of alternatives that achieve the same effect are also possible, some of which correspond to specific vulnerabilities that have affected Git in the past:

• A tree or blob whose name contains one or more /, to traverse upward or downward. For example, even without containing any tree named .. or .git, a repository can represent a file named ../outside or .git/hooks/pre-commit. This is distinct from the more intuitive case a repository containing trees that represent those paths.
• In Windows, a tree or blob whose name contains one or more \, to traverse upward or downward. (Unlike /, these are valid on other systems.) See GHSA-xjx4-8694-q2fq.
• On a case-insensitive filesystem (such as NTFS, APFS, or HFS+), a tree named as a case variant of .git.
• On HFS+, a tree named like .git or a case variant, with characters added that HFS+ ignores in collation. See https://github.com/git/git/commit/6162a1d323d24fd8cbbb1a6145a91fb849b2568f.
• On NTFS, a tree equivalent to .git (or a case variant) by the use of NTFS stream notation, such as .git::$INDEX_ALLOCATION. See GHSA-5wph-8frv-58vj.
• On an NTFS volume with 8.3 aliasing enabled, a tree named as git~1 (or a case variant). See GHSA-589j-mmg9-733v.

When a checkout creates some files outside the repository directory but fails to complete, the repository directory is usually removed, but the outside files remain.

PoC

For simplicity, these examples stage a stand-in file with a valid name, modify the index, and commit. The instructions assume sed supports -i, which is the case on most systems. If using Windows, a Git Bash shell should be used.

Example: Downward traversal to install hooks

1. Create a new repository with git init dangerous-repo-installs-hook and cd into the directory.
2. Create the stand-in called .git@hooks@pre-commit, with the contents:

   #!/bin/sh
   printf 'Vulnerable!\n'
   date >vulnerable
   

3. Stage the stand-in: git add --chmod=+x .git@hooks@pre-commit
4. Edit the index: env LC_ALL=C sed -i.orig 's|\.git@hooks@pre-commit|.git/hooks/pre-commit|' .git/index
5. Commit: git commit -m 'Initial commit'
6. Optionally, push to a private remote.

Then, on another or the same machine:

1. Clone the repository with a gix clone … command.
2. Enter the newly created directory.
3. Optionally run ls -l .git/hooks to observe that the pre-commit hook is already present.
4. Make a new file and commit it with git. This causes the payload surreptitiously installed as a pre-commit hook to run, printing the message Vulnerable! and creating a file in the current directory containing the current date and time.

Note that the effect is not limited to modifying the current directory. The payload could be written to perform any action that the user who runs git commit is capable of.

Example: Upward traversal to create a file above the working tree

1. Create a new repository with git init dangerous-repo-reaches-up, and cd into the directory.
2. Create the stand-in: echo 'A file outside the working tree, somehow.' >..@outside
3. Stage the stand-in: git add ..@outside
4. Edit the index: env LC_ALL=C sed -i.orig 's|\.\.@outside|../outside|' .git/index
5. Commit: git commit -m 'Initial commit'
6. Optionally, push to a private remote.

Then, as above, on the same or another machine, clone the repository with a gix clone … command. Observe that a file named outside is present alongside (not inside) the cloned directory.

Impact

Any use of gix or another application that makes use of gix-worktree-state, or otherwise relies on gix-fs and gix-worktree for validation, is affected, if used to clone untrusted repositories. The above description focuses on code execution, as that leads to a complete loss of confidentiality, integrity, and availability, but creating files outside a working tree without attempting to execute code can directly impact integrity as well.

In use cases where no untrusted repository is ever cloned, this vulnerability has no impact. Furthermore, the impact of this vulnerability may be lower when gix is used to clone a repository for CI/CD purposes, even if untrusted, since in such uses the environment is usually isolated and arbitrary code is usually run deliberately from the repository with necessary safeguards in place.

Summary

A malicious tree can be constructed that will, when checked out with gitoxide, permit writing an attacker-controlled symlink into any existing directory the user has write access to.

Details

During checkout, all symlink index entries are deferred and created after regular files using a single shared gix_worktree::Stack. Internally, this uses a gix_fs::Stack.

gix_fs::Stack::make_relative_path_current() caches validated path prefixes: when the previously-processed leaf component exactly matches the leading component(s) of the next path, the leaf-to-directory transition at gix-fs/src/stack.rs:195-197 invokes only delegate.push_directory(), never delegate.push().

In gix_worktree::stack::delegate::StackDelegate, when the state member is State::CreateDirectoryAndAttributesStack, Attributes::push_directory() only loads attributes (from the ODB, in the clone case), and does not perform any other checks. The on-disk symlink_metadata() check and unlink-on-collision live in StackDelegate::push()'s invocation of create_leading_directory(), which is therefore bypassed for the cached prefix. The final symlink is created with plain std::os::unix::fs::symlink, which follows symlinks in parent directories.

Therefore, it's possible to provide a tree with duplicate symlink and directory entries that exploits this. If a tree is constructed with:

1. A 120000 (symlink) entry a that points to .git/hooks.
2. A 040000 (directory) entry a with a subtree that contains a symlink from post-checkout to ../../payload.
3. A 100755 (executable file) entry payload.

This is converted by gix_index::State::from_tree() into index entries ["a" (SYMLINK), "a/post-checkout" (SYMLINK)].

Then, during the delayed symlink phase:

1. a is created as a symlink to e.g. .git/hooks.
2. When processing a/post-checkout, the a prefix is reused from the just-processed leaf entry without re-running the intermediate-directory check, after which…
3. symlink(target, "<wt>/a/post-checkout") resolves through the just-created symlink to write .git/hooks/post-checkout.

Although this example uses .git/hooks for simplicity, there's no actual requirement to write within the repo checkout. This can be fairly easily chained into code execution by writing to something that is known to be executed — for example, by writing to .git/hooks/post-checkout if the attacker knows that a hook-aware Git implementation will be used later, or by writing to something like ~/.local/bin.

PoC

Attached is build-bad-repo.sh, which builds a repo with the aforementioned tree structure. Cloning it with gix will set up the malicious .git/hooks/post-checkout, at which point anything that normally invokes the post-checkout hook will result in its execution, such as git checkout -b new-branch.

Impact

Arbitrary symlink creation into any existing directory the user can write to.

Disclosure

This vulnerability was found by AI (specifically, Claude Mythos) as part of Project Glasswing. This advisory was written and verified by a human.

Summary

During checkout, gitoxide does not verify that paths point to locations in the working tree. A specially crafted repository can, when cloned, place new files anywhere writable by the application.

Details

Although gix-worktree-state checks for collisions with existing files, it does not itself check if a path is really in the working tree when performing a checkout, nor do the path checks in gix-fs and gix-worktree prevent this. Cloning an untrusted repository containing specially crafted tree or blob names will create new files outside the repository, or inside the repository or a submodule's .git directory. The simplest cases are:

• A tree named .. to traverse upward. This facilitates arbitrary code execution because files can be placed in one or more locations where they are likely to be executed soon.
• A tree named .git to enter a .git directory. This facilitates arbitrary code execution because hooks can be installed.

A number of alternatives that achieve the same effect are also possible, some of which correspond to specific vulnerabilities that have affected Git in the past:

• A tree or blob whose name contains one or more /, to traverse upward or downward. For example, even without containing any tree named .. or .git, a repository can represent a file named ../outside or .git/hooks/pre-commit. This is distinct from the more intuitive case a repository containing trees that represent those paths.
• In Windows, a tree or blob whose name contains one or more \, to traverse upward or downward. (Unlike /, these are valid on other systems.) See GHSA-xjx4-8694-q2fq.
• On a case-insensitive filesystem (such as NTFS, APFS, or HFS+), a tree named as a case variant of .git.
• On HFS+, a tree named like .git or a case variant, with characters added that HFS+ ignores in collation. See https://github.com/git/git/commit/6162a1d323d24fd8cbbb1a6145a91fb849b2568f.
• On NTFS, a tree equivalent to .git (or a case variant) by the use of NTFS stream notation, such as .git::$INDEX_ALLOCATION. See GHSA-5wph-8frv-58vj.
• On an NTFS volume with 8.3 aliasing enabled, a tree named as git~1 (or a case variant). See GHSA-589j-mmg9-733v.

When a checkout creates some files outside the repository directory but fails to complete, the repository directory is usually removed, but the outside files remain.

PoC

For simplicity, these examples stage a stand-in file with a valid name, modify the index, and commit. The instructions assume sed supports -i, which is the case on most systems. If using Windows, a Git Bash shell should be used.

Example: Downward traversal to install hooks

1. Create a new repository with git init dangerous-repo-installs-hook and cd into the directory.
2. Create the stand-in called .git@hooks@pre-commit, with the contents:

   #!/bin/sh
   printf 'Vulnerable!\n'
   date >vulnerable
   

3. Stage the stand-in: git add --chmod=+x .git@hooks@pre-commit
4. Edit the index: env LC_ALL=C sed -i.orig 's|\.git@hooks@pre-commit|.git/hooks/pre-commit|' .git/index
5. Commit: git commit -m 'Initial commit'
6. Optionally, push to a private remote.

Then, on another or the same machine:

1. Clone the repository with a gix clone … command.
2. Enter the newly created directory.
3. Optionally run ls -l .git/hooks to observe that the pre-commit hook is already present.
4. Make a new file and commit it with git. This causes the payload surreptitiously installed as a pre-commit hook to run, printing the message Vulnerable! and creating a file in the current directory containing the current date and time.

Note that the effect is not limited to modifying the current directory. The payload could be written to perform any action that the user who runs git commit is capable of.

Example: Upward traversal to create a file above the working tree

1. Create a new repository with git init dangerous-repo-reaches-up, and cd into the directory.
2. Create the stand-in: echo 'A file outside the working tree, somehow.' >..@outside
3. Stage the stand-in: git add ..@outside
4. Edit the index: env LC_ALL=C sed -i.orig 's|\.\.@outside|../outside|' .git/index
5. Commit: git commit -m 'Initial commit'
6. Optionally, push to a private remote.

Then, as above, on the same or another machine, clone the repository with a gix clone … command. Observe that a file named outside is present alongside (not inside) the cloned directory.

Impact

Any use of gix or another application that makes use of gix-worktree-state, or otherwise relies on gix-fs and gix-worktree for validation, is affected, if used to clone untrusted repositories. The above description focuses on code execution, as that leads to a complete loss of confidentiality, integrity, and availability, but creating files outside a working tree without attempting to execute code can directly impact integrity as well.

In use cases where no untrusted repository is ever cloned, this vulnerability has no impact. Furthermore, the impact of this vulnerability may be lower when gix is used to clone a repository for CI/CD purposes, even if untrusted, since in such uses the environment is usually isolated and arbitrary code is usually run deliberately from the repository with necessary safeguards in place.

Summary

A malicious tree can be constructed that will, when checked out with gitoxide, permit writing an attacker-controlled symlink into any existing directory the user has write access to.

Details

During checkout, all symlink index entries are deferred and created after regular files using a single shared gix_worktree::Stack. Internally, this uses a gix_fs::Stack.

gix_fs::Stack::make_relative_path_current() caches validated path prefixes: when the previously-processed leaf component exactly matches the leading component(s) of the next path, the leaf-to-directory transition at gix-fs/src/stack.rs:195-197 invokes only delegate.push_directory(), never delegate.push().

In gix_worktree::stack::delegate::StackDelegate, when the state member is State::CreateDirectoryAndAttributesStack, Attributes::push_directory() only loads attributes (from the ODB, in the clone case), and does not perform any other checks. The on-disk symlink_metadata() check and unlink-on-collision live in StackDelegate::push()'s invocation of create_leading_directory(), which is therefore bypassed for the cached prefix. The final symlink is created with plain std::os::unix::fs::symlink, which follows symlinks in parent directories.

Therefore, it's possible to provide a tree with duplicate symlink and directory entries that exploits this. If a tree is constructed with:

1. A 120000 (symlink) entry a that points to .git/hooks.
2. A 040000 (directory) entry a with a subtree that contains a symlink from post-checkout to ../../payload.
3. A 100755 (executable file) entry payload.

This is converted by gix_index::State::from_tree() into index entries ["a" (SYMLINK), "a/post-checkout" (SYMLINK)].

Then, during the delayed symlink phase:

1. a is created as a symlink to e.g. .git/hooks.
2. When processing a/post-checkout, the a prefix is reused from the just-processed leaf entry without re-running the intermediate-directory check, after which…
3. symlink(target, "<wt>/a/post-checkout") resolves through the just-created symlink to write .git/hooks/post-checkout.

Although this example uses .git/hooks for simplicity, there's no actual requirement to write within the repo checkout. This can be fairly easily chained into code execution by writing to something that is known to be executed — for example, by writing to .git/hooks/post-checkout if the attacker knows that a hook-aware Git implementation will be used later, or by writing to something like ~/.local/bin.

PoC

Attached is build-bad-repo.sh, which builds a repo with the aforementioned tree structure. Cloning it with gix will set up the malicious .git/hooks/post-checkout, at which point anything that normally invokes the post-checkout hook will result in its execution, such as git checkout -b new-branch.

Impact

Arbitrary symlink creation into any existing directory the user can write to.

Disclosure

This vulnerability was found by AI (specifically, Claude Mythos) as part of Project Glasswing. This advisory was written and verified by a human.

Summary

During checkout, gitoxide does not verify that paths point to locations in the working tree. A specially crafted repository can, when cloned, place new files anywhere writable by the application.

Details

Although gix-worktree-state checks for collisions with existing files, it does not itself check if a path is really in the working tree when performing a checkout, nor do the path checks in gix-fs and gix-worktree prevent this. Cloning an untrusted repository containing specially crafted tree or blob names will create new files outside the repository, or inside the repository or a submodule's .git directory. The simplest cases are:

• A tree named .. to traverse upward. This facilitates arbitrary code execution because files can be placed in one or more locations where they are likely to be executed soon.
• A tree named .git to enter a .git directory. This facilitates arbitrary code execution because hooks can be installed.

A number of alternatives that achieve the same effect are also possible, some of which correspond to specific vulnerabilities that have affected Git in the past:

• A tree or blob whose name contains one or more /, to traverse upward or downward. For example, even without containing any tree named .. or .git, a repository can represent a file named ../outside or .git/hooks/pre-commit. This is distinct from the more intuitive case a repository containing trees that represent those paths.
• In Windows, a tree or blob whose name contains one or more \, to traverse upward or downward. (Unlike /, these are valid on other systems.) See GHSA-xjx4-8694-q2fq.
• On a case-insensitive filesystem (such as NTFS, APFS, or HFS+), a tree named as a case variant of .git.
• On HFS+, a tree named like .git or a case variant, with characters added that HFS+ ignores in collation. See https://github.com/git/git/commit/6162a1d323d24fd8cbbb1a6145a91fb849b2568f.
• On NTFS, a tree equivalent to .git (or a case variant) by the use of NTFS stream notation, such as .git::$INDEX_ALLOCATION. See GHSA-5wph-8frv-58vj.
• On an NTFS volume with 8.3 aliasing enabled, a tree named as git~1 (or a case variant). See GHSA-589j-mmg9-733v.

When a checkout creates some files outside the repository directory but fails to complete, the repository directory is usually removed, but the outside files remain.

PoC

For simplicity, these examples stage a stand-in file with a valid name, modify the index, and commit. The instructions assume sed supports -i, which is the case on most systems. If using Windows, a Git Bash shell should be used.

Example: Downward traversal to install hooks

1. Create a new repository with git init dangerous-repo-installs-hook and cd into the directory.
2. Create the stand-in called .git@hooks@pre-commit, with the contents:

   #!/bin/sh
   printf 'Vulnerable!\n'
   date >vulnerable
   

3. Stage the stand-in: git add --chmod=+x .git@hooks@pre-commit
4. Edit the index: env LC_ALL=C sed -i.orig 's|\.git@hooks@pre-commit|.git/hooks/pre-commit|' .git/index
5. Commit: git commit -m 'Initial commit'
6. Optionally, push to a private remote.

Then, on another or the same machine:

1. Clone the repository with a gix clone … command.
2. Enter the newly created directory.
3. Optionally run ls -l .git/hooks to observe that the pre-commit hook is already present.
4. Make a new file and commit it with git. This causes the payload surreptitiously installed as a pre-commit hook to run, printing the message Vulnerable! and creating a file in the current directory containing the current date and time.

Note that the effect is not limited to modifying the current directory. The payload could be written to perform any action that the user who runs git commit is capable of.

Example: Upward traversal to create a file above the working tree

1. Create a new repository with git init dangerous-repo-reaches-up, and cd into the directory.
2. Create the stand-in: echo 'A file outside the working tree, somehow.' >..@outside
3. Stage the stand-in: git add ..@outside
4. Edit the index: env LC_ALL=C sed -i.orig 's|\.\.@outside|../outside|' .git/index
5. Commit: git commit -m 'Initial commit'
6. Optionally, push to a private remote.

Then, as above, on the same or another machine, clone the repository with a gix clone … command. Observe that a file named outside is present alongside (not inside) the cloned directory.

Impact

Any use of gix or another application that makes use of gix-worktree-state, or otherwise relies on gix-fs and gix-worktree for validation, is affected, if used to clone untrusted repositories. The above description focuses on code execution, as that leads to a complete loss of confidentiality, integrity, and availability, but creating files outside a working tree without attempting to execute code can directly impact integrity as well.

In use cases where no untrusted repository is ever cloned, this vulnerability has no impact. Furthermore, the impact of this vulnerability may be lower when gix is used to clone a repository for CI/CD purposes, even if untrusted, since in such uses the environment is usually isolated and arbitrary code is usually run deliberately from the repository with necessary safeguards in place.

Summary

A malicious tree can be constructed that will, when checked out with gitoxide, permit writing an attacker-controlled symlink into any existing directory the user has write access to.

Details

During checkout, all symlink index entries are deferred and created after regular files using a single shared gix_worktree::Stack. Internally, this uses a gix_fs::Stack.

gix_fs::Stack::make_relative_path_current() caches validated path prefixes: when the previously-processed leaf component exactly matches the leading component(s) of the next path, the leaf-to-directory transition at gix-fs/src/stack.rs:195-197 invokes only delegate.push_directory(), never delegate.push().

In gix_worktree::stack::delegate::StackDelegate, when the state member is State::CreateDirectoryAndAttributesStack, Attributes::push_directory() only loads attributes (from the ODB, in the clone case), and does not perform any other checks. The on-disk symlink_metadata() check and unlink-on-collision live in StackDelegate::push()'s invocation of create_leading_directory(), which is therefore bypassed for the cached prefix. The final symlink is created with plain std::os::unix::fs::symlink, which follows symlinks in parent directories.

Therefore, it's possible to provide a tree with duplicate symlink and directory entries that exploits this. If a tree is constructed with:

1. A 120000 (symlink) entry a that points to .git/hooks.
2. A 040000 (directory) entry a with a subtree that contains a symlink from post-checkout to ../../payload.
3. A 100755 (executable file) entry payload.

This is converted by gix_index::State::from_tree() into index entries ["a" (SYMLINK), "a/post-checkout" (SYMLINK)].

Then, during the delayed symlink phase:

1. a is created as a symlink to e.g. .git/hooks.
2. When processing a/post-checkout, the a prefix is reused from the just-processed leaf entry without re-running the intermediate-directory check, after which…
3. symlink(target, "<wt>/a/post-checkout") resolves through the just-created symlink to write .git/hooks/post-checkout.

Although this example uses .git/hooks for simplicity, there's no actual requirement to write within the repo checkout. This can be fairly easily chained into code execution by writing to something that is known to be executed — for example, by writing to .git/hooks/post-checkout if the attacker knows that a hook-aware Git implementation will be used later, or by writing to something like ~/.local/bin.

PoC

Attached is build-bad-repo.sh, which builds a repo with the aforementioned tree structure. Cloning it with gix will set up the malicious .git/hooks/post-checkout, at which point anything that normally invokes the post-checkout hook will result in its execution, such as git checkout -b new-branch.

Impact

Arbitrary symlink creation into any existing directory the user can write to.

Disclosure

This vulnerability was found by AI (specifically, Claude Mythos) as part of Project Glasswing. This advisory was written and verified by a human.

Summary

During checkout, gitoxide does not verify that paths point to locations in the working tree. A specially crafted repository can, when cloned, place new files anywhere writable by the application.

Details

Although gix-worktree-state checks for collisions with existing files, it does not itself check if a path is really in the working tree when performing a checkout, nor do the path checks in gix-fs and gix-worktree prevent this. Cloning an untrusted repository containing specially crafted tree or blob names will create new files outside the repository, or inside the repository or a submodule's .git directory. The simplest cases are:

• A tree named .. to traverse upward. This facilitates arbitrary code execution because files can be placed in one or more locations where they are likely to be executed soon.
• A tree named .git to enter a .git directory. This facilitates arbitrary code execution because hooks can be installed.

A number of alternatives that achieve the same effect are also possible, some of which correspond to specific vulnerabilities that have affected Git in the past:

• A tree or blob whose name contains one or more /, to traverse upward or downward. For example, even without containing any tree named .. or .git, a repository can represent a file named ../outside or .git/hooks/pre-commit. This is distinct from the more intuitive case a repository containing trees that represent those paths.
• In Windows, a tree or blob whose name contains one or more \, to traverse upward or downward. (Unlike /, these are valid on other systems.) See GHSA-xjx4-8694-q2fq.
• On a case-insensitive filesystem (such as NTFS, APFS, or HFS+), a tree named as a case variant of .git.
• On HFS+, a tree named like .git or a case variant, with characters added that HFS+ ignores in collation. See https://github.com/git/git/commit/6162a1d323d24fd8cbbb1a6145a91fb849b2568f.
• On NTFS, a tree equivalent to .git (or a case variant) by the use of NTFS stream notation, such as .git::$INDEX_ALLOCATION. See GHSA-5wph-8frv-58vj.
• On an NTFS volume with 8.3 aliasing enabled, a tree named as git~1 (or a case variant). See GHSA-589j-mmg9-733v.

When a checkout creates some files outside the repository directory but fails to complete, the repository directory is usually removed, but the outside files remain.

PoC

For simplicity, these examples stage a stand-in file with a valid name, modify the index, and commit. The instructions assume sed supports -i, which is the case on most systems. If using Windows, a Git Bash shell should be used.

Example: Downward traversal to install hooks

1. Create a new repository with git init dangerous-repo-installs-hook and cd into the directory.
2. Create the stand-in called .git@hooks@pre-commit, with the contents:

   #!/bin/sh
   printf 'Vulnerable!\n'
   date >vulnerable
   

3. Stage the stand-in: git add --chmod=+x .git@hooks@pre-commit
4. Edit the index: env LC_ALL=C sed -i.orig 's|\.git@hooks@pre-commit|.git/hooks/pre-commit|' .git/index
5. Commit: git commit -m 'Initial commit'
6. Optionally, push to a private remote.

Then, on another or the same machine:

1. Clone the repository with a gix clone … command.
2. Enter the newly created directory.
3. Optionally run ls -l .git/hooks to observe that the pre-commit hook is already present.
4. Make a new file and commit it with git. This causes the payload surreptitiously installed as a pre-commit hook to run, printing the message Vulnerable! and creating a file in the current directory containing the current date and time.

Note that the effect is not limited to modifying the current directory. The payload could be written to perform any action that the user who runs git commit is capable of.

Example: Upward traversal to create a file above the working tree

1. Create a new repository with git init dangerous-repo-reaches-up, and cd into the directory.
2. Create the stand-in: echo 'A file outside the working tree, somehow.' >..@outside
3. Stage the stand-in: git add ..@outside
4. Edit the index: env LC_ALL=C sed -i.orig 's|\.\.@outside|../outside|' .git/index
5. Commit: git commit -m 'Initial commit'
6. Optionally, push to a private remote.

Then, as above, on the same or another machine, clone the repository with a gix clone … command. Observe that a file named outside is present alongside (not inside) the cloned directory.

Impact

Any use of gix or another application that makes use of gix-worktree-state, or otherwise relies on gix-fs and gix-worktree for validation, is affected, if used to clone untrusted repositories. The above description focuses on code execution, as that leads to a complete loss of confidentiality, integrity, and availability, but creating files outside a working tree without attempting to execute code can directly impact integrity as well.

In use cases where no untrusted repository is ever cloned, this vulnerability has no impact. Furthermore, the impact of this vulnerability may be lower when gix is used to clone a repository for CI/CD purposes, even if untrusted, since in such uses the environment is usually isolated and arbitrary code is usually run deliberately from the repository with necessary safeguards in place.

Summary

A malicious tree can be constructed that will, when checked out with gitoxide, permit writing an attacker-controlled symlink into any existing directory the user has write access to.

Details

During checkout, all symlink index entries are deferred and created after regular files using a single shared gix_worktree::Stack. Internally, this uses a gix_fs::Stack.

gix_fs::Stack::make_relative_path_current() caches validated path prefixes: when the previously-processed leaf component exactly matches the leading component(s) of the next path, the leaf-to-directory transition at gix-fs/src/stack.rs:195-197 invokes only delegate.push_directory(), never delegate.push().

In gix_worktree::stack::delegate::StackDelegate, when the state member is State::CreateDirectoryAndAttributesStack, Attributes::push_directory() only loads attributes (from the ODB, in the clone case), and does not perform any other checks. The on-disk symlink_metadata() check and unlink-on-collision live in StackDelegate::push()'s invocation of create_leading_directory(), which is therefore bypassed for the cached prefix. The final symlink is created with plain std::os::unix::fs::symlink, which follows symlinks in parent directories.

Therefore, it's possible to provide a tree with duplicate symlink and directory entries that exploits this. If a tree is constructed with:

1. A 120000 (symlink) entry a that points to .git/hooks.
2. A 040000 (directory) entry a with a subtree that contains a symlink from post-checkout to ../../payload.
3. A 100755 (executable file) entry payload.

This is converted by gix_index::State::from_tree() into index entries ["a" (SYMLINK), "a/post-checkout" (SYMLINK)].

Then, during the delayed symlink phase:

1. a is created as a symlink to e.g. .git/hooks.
2. When processing a/post-checkout, the a prefix is reused from the just-processed leaf entry without re-running the intermediate-directory check, after which…
3. symlink(target, "<wt>/a/post-checkout") resolves through the just-created symlink to write .git/hooks/post-checkout.

Although this example uses .git/hooks for simplicity, there's no actual requirement to write within the repo checkout. This can be fairly easily chained into code execution by writing to something that is known to be executed — for example, by writing to .git/hooks/post-checkout if the attacker knows that a hook-aware Git implementation will be used later, or by writing to something like ~/.local/bin.

PoC

Attached is build-bad-repo.sh, which builds a repo with the aforementioned tree structure. Cloning it with gix will set up the malicious .git/hooks/post-checkout, at which point anything that normally invokes the post-checkout hook will result in its execution, such as git checkout -b new-branch.

Impact

Arbitrary symlink creation into any existing directory the user can write to.

Disclosure

This vulnerability was found by AI (specifically, Claude Mythos) as part of Project Glasswing. This advisory was written and verified by a human.

Summary

During checkout, gitoxide does not verify that paths point to locations in the working tree. A specially crafted repository can, when cloned, place new files anywhere writable by the application.

Details

Although gix-worktree-state checks for collisions with existing files, it does not itself check if a path is really in the working tree when performing a checkout, nor do the path checks in gix-fs and gix-worktree prevent this. Cloning an untrusted repository containing specially crafted tree or blob names will create new files outside the repository, or inside the repository or a submodule's .git directory. The simplest cases are:

• A tree named .. to traverse upward. This facilitates arbitrary code execution because files can be placed in one or more locations where they are likely to be executed soon.
• A tree named .git to enter a .git directory. This facilitates arbitrary code execution because hooks can be installed.

A number of alternatives that achieve the same effect are also possible, some of which correspond to specific vulnerabilities that have affected Git in the past:

• A tree or blob whose name contains one or more /, to traverse upward or downward. For example, even without containing any tree named .. or .git, a repository can represent a file named ../outside or .git/hooks/pre-commit. This is distinct from the more intuitive case a repository containing trees that represent those paths.
• In Windows, a tree or blob whose name contains one or more \, to traverse upward or downward. (Unlike /, these are valid on other systems.) See GHSA-xjx4-8694-q2fq.
• On a case-insensitive filesystem (such as NTFS, APFS, or HFS+), a tree named as a case variant of .git.
• On HFS+, a tree named like .git or a case variant, with characters added that HFS+ ignores in collation. See https://github.com/git/git/commit/6162a1d323d24fd8cbbb1a6145a91fb849b2568f.
• On NTFS, a tree equivalent to .git (or a case variant) by the use of NTFS stream notation, such as .git::$INDEX_ALLOCATION. See GHSA-5wph-8frv-58vj.
• On an NTFS volume with 8.3 aliasing enabled, a tree named as git~1 (or a case variant). See GHSA-589j-mmg9-733v.

When a checkout creates some files outside the repository directory but fails to complete, the repository directory is usually removed, but the outside files remain.

PoC

For simplicity, these examples stage a stand-in file with a valid name, modify the index, and commit. The instructions assume sed supports -i, which is the case on most systems. If using Windows, a Git Bash shell should be used.

Example: Downward traversal to install hooks

1. Create a new repository with git init dangerous-repo-installs-hook and cd into the directory.
2. Create the stand-in called .git@hooks@pre-commit, with the contents:

   #!/bin/sh
   printf 'Vulnerable!\n'
   date >vulnerable
   

3. Stage the stand-in: git add --chmod=+x .git@hooks@pre-commit
4. Edit the index: env LC_ALL=C sed -i.orig 's|\.git@hooks@pre-commit|.git/hooks/pre-commit|' .git/index
5. Commit: git commit -m 'Initial commit'
6. Optionally, push to a private remote.

Then, on another or the same machine:

1. Clone the repository with a gix clone … command.
2. Enter the newly created directory.
3. Optionally run ls -l .git/hooks to observe that the pre-commit hook is already present.
4. Make a new file and commit it with git. This causes the payload surreptitiously installed as a pre-commit hook to run, printing the message Vulnerable! and creating a file in the current directory containing the current date and time.

Note that the effect is not limited to modifying the current directory. The payload could be written to perform any action that the user who runs git commit is capable of.

Example: Upward traversal to create a file above the working tree

1. Create a new repository with git init dangerous-repo-reaches-up, and cd into the directory.
2. Create the stand-in: echo 'A file outside the working tree, somehow.' >..@outside
3. Stage the stand-in: git add ..@outside
4. Edit the index: env LC_ALL=C sed -i.orig 's|\.\.@outside|../outside|' .git/index
5. Commit: git commit -m 'Initial commit'
6. Optionally, push to a private remote.

Then, as above, on the same or another machine, clone the repository with a gix clone … command. Observe that a file named outside is present alongside (not inside) the cloned directory.

Impact

Any use of gix or another application that makes use of gix-worktree-state, or otherwise relies on gix-fs and gix-worktree for validation, is affected, if used to clone untrusted repositories. The above description focuses on code execution, as that leads to a complete loss of confidentiality, integrity, and availability, but creating files outside a working tree without attempting to execute code can directly impact integrity as well.

In use cases where no untrusted repository is ever cloned, this vulnerability has no impact. Furthermore, the impact of this vulnerability may be lower when gix is used to clone a repository for CI/CD purposes, even if untrusted, since in such uses the environment is usually isolated and arbitrary code is usually run deliberately from the repository with necessary safeguards in place.

Summary

A malicious tree can be constructed that will, when checked out with gitoxide, permit writing an attacker-controlled symlink into any existing directory the user has write access to.

Details

During checkout, all symlink index entries are deferred and created after regular files using a single shared gix_worktree::Stack. Internally, this uses a gix_fs::Stack.

gix_fs::Stack::make_relative_path_current() caches validated path prefixes: when the previously-processed leaf component exactly matches the leading component(s) of the next path, the leaf-to-directory transition at gix-fs/src/stack.rs:195-197 invokes only delegate.push_directory(), never delegate.push().

In gix_worktree::stack::delegate::StackDelegate, when the state member is State::CreateDirectoryAndAttributesStack, Attributes::push_directory() only loads attributes (from the ODB, in the clone case), and does not perform any other checks. The on-disk symlink_metadata() check and unlink-on-collision live in StackDelegate::push()'s invocation of create_leading_directory(), which is therefore bypassed for the cached prefix. The final symlink is created with plain std::os::unix::fs::symlink, which follows symlinks in parent directories.

Therefore, it's possible to provide a tree with duplicate symlink and directory entries that exploits this. If a tree is constructed with:

1. A 120000 (symlink) entry a that points to .git/hooks.
2. A 040000 (directory) entry a with a subtree that contains a symlink from post-checkout to ../../payload.
3. A 100755 (executable file) entry payload.

This is converted by gix_index::State::from_tree() into index entries ["a" (SYMLINK), "a/post-checkout" (SYMLINK)].

Then, during the delayed symlink phase:

1. a is created as a symlink to e.g. .git/hooks.
2. When processing a/post-checkout, the a prefix is reused from the just-processed leaf entry without re-running the intermediate-directory check, after which…
3. symlink(target, "<wt>/a/post-checkout") resolves through the just-created symlink to write .git/hooks/post-checkout.

Although this example uses .git/hooks for simplicity, there's no actual requirement to write within the repo checkout. This can be fairly easily chained into code execution by writing to something that is known to be executed — for example, by writing to .git/hooks/post-checkout if the attacker knows that a hook-aware Git implementation will be used later, or by writing to something like ~/.local/bin.

PoC

Attached is build-bad-repo.sh, which builds a repo with the aforementioned tree structure. Cloning it with gix will set up the malicious .git/hooks/post-checkout, at which point anything that normally invokes the post-checkout hook will result in its execution, such as git checkout -b new-branch.

Impact

Arbitrary symlink creation into any existing directory the user can write to.

Disclosure

This vulnerability was found by AI (specifically, Claude Mythos) as part of Project Glasswing. This advisory was written and verified by a human.

Summary

During checkout, gitoxide does not verify that paths point to locations in the working tree. A specially crafted repository can, when cloned, place new files anywhere writable by the application.

Details

Although gix-worktree-state checks for collisions with existing files, it does not itself check if a path is really in the working tree when performing a checkout, nor do the path checks in gix-fs and gix-worktree prevent this. Cloning an untrusted repository containing specially crafted tree or blob names will create new files outside the repository, or inside the repository or a submodule's .git directory. The simplest cases are:

• A tree named .. to traverse upward. This facilitates arbitrary code execution because files can be placed in one or more locations where they are likely to be executed soon.
• A tree named .git to enter a .git directory. This facilitates arbitrary code execution because hooks can be installed.

A number of alternatives that achieve the same effect are also possible, some of which correspond to specific vulnerabilities that have affected Git in the past:

• A tree or blob whose name contains one or more /, to traverse upward or downward. For example, even without containing any tree named .. or .git, a repository can represent a file named ../outside or .git/hooks/pre-commit. This is distinct from the more intuitive case a repository containing trees that represent those paths.
• In Windows, a tree or blob whose name contains one or more \, to traverse upward or downward. (Unlike /, these are valid on other systems.) See GHSA-xjx4-8694-q2fq.
• On a case-insensitive filesystem (such as NTFS, APFS, or HFS+), a tree named as a case variant of .git.
• On HFS+, a tree named like .git or a case variant, with characters added that HFS+ ignores in collation. See https://github.com/git/git/commit/6162a1d323d24fd8cbbb1a6145a91fb849b2568f.
• On NTFS, a tree equivalent to .git (or a case variant) by the use of NTFS stream notation, such as .git::$INDEX_ALLOCATION. See GHSA-5wph-8frv-58vj.
• On an NTFS volume with 8.3 aliasing enabled, a tree named as git~1 (or a case variant). See GHSA-589j-mmg9-733v.

When a checkout creates some files outside the repository directory but fails to complete, the repository directory is usually removed, but the outside files remain.

PoC

For simplicity, these examples stage a stand-in file with a valid name, modify the index, and commit. The instructions assume sed supports -i, which is the case on most systems. If using Windows, a Git Bash shell should be used.

Example: Downward traversal to install hooks

1. Create a new repository with git init dangerous-repo-installs-hook and cd into the directory.
2. Create the stand-in called .git@hooks@pre-commit, with the contents:

   #!/bin/sh
   printf 'Vulnerable!\n'
   date >vulnerable
   

3. Stage the stand-in: git add --chmod=+x .git@hooks@pre-commit
4. Edit the index: env LC_ALL=C sed -i.orig 's|\.git@hooks@pre-commit|.git/hooks/pre-commit|' .git/index
5. Commit: git commit -m 'Initial commit'
6. Optionally, push to a private remote.

Then, on another or the same machine:

1. Clone the repository with a gix clone … command.
2. Enter the newly created directory.
3. Optionally run ls -l .git/hooks to observe that the pre-commit hook is already present.
4. Make a new file and commit it with git. This causes the payload surreptitiously installed as a pre-commit hook to run, printing the message Vulnerable! and creating a file in the current directory containing the current date and time.

Note that the effect is not limited to modifying the current directory. The payload could be written to perform any action that the user who runs git commit is capable of.

Example: Upward traversal to create a file above the working tree

1. Create a new repository with git init dangerous-repo-reaches-up, and cd into the directory.
2. Create the stand-in: echo 'A file outside the working tree, somehow.' >..@outside
3. Stage the stand-in: git add ..@outside
4. Edit the index: env LC_ALL=C sed -i.orig 's|\.\.@outside|../outside|' .git/index
5. Commit: git commit -m 'Initial commit'
6. Optionally, push to a private remote.

Then, as above, on the same or another machine, clone the repository with a gix clone … command. Observe that a file named outside is present alongside (not inside) the cloned directory.

Impact

Any use of gix or another application that makes use of gix-worktree-state, or otherwise relies on gix-fs and gix-worktree for validation, is affected, if used to clone untrusted repositories. The above description focuses on code execution, as that leads to a complete loss of confidentiality, integrity, and availability, but creating files outside a working tree without attempting to execute code can directly impact integrity as well.

In use cases where no untrusted repository is ever cloned, this vulnerability has no impact. Furthermore, the impact of this vulnerability may be lower when gix is used to clone a repository for CI/CD purposes, even if untrusted, since in such uses the environment is usually isolated and arbitrary code is usually run deliberately from the repository with necessary safeguards in place.

Summary

A malicious tree can be constructed that will, when checked out with gitoxide, permit writing an attacker-controlled symlink into any existing directory the user has write access to.

Details

During checkout, all symlink index entries are deferred and created after regular files using a single shared gix_worktree::Stack. Internally, this uses a gix_fs::Stack.

gix_fs::Stack::make_relative_path_current() caches validated path prefixes: when the previously-processed leaf component exactly matches the leading component(s) of the next path, the leaf-to-directory transition at gix-fs/src/stack.rs:195-197 invokes only delegate.push_directory(), never delegate.push().

In gix_worktree::stack::delegate::StackDelegate, when the state member is State::CreateDirectoryAndAttributesStack, Attributes::push_directory() only loads attributes (from the ODB, in the clone case), and does not perform any other checks. The on-disk symlink_metadata() check and unlink-on-collision live in StackDelegate::push()'s invocation of create_leading_directory(), which is therefore bypassed for the cached prefix. The final symlink is created with plain std::os::unix::fs::symlink, which follows symlinks in parent directories.

Therefore, it's possible to provide a tree with duplicate symlink and directory entries that exploits this. If a tree is constructed with:

1. A 120000 (symlink) entry a that points to .git/hooks.
2. A 040000 (directory) entry a with a subtree that contains a symlink from post-checkout to ../../payload.
3. A 100755 (executable file) entry payload.

This is converted by gix_index::State::from_tree() into index entries ["a" (SYMLINK), "a/post-checkout" (SYMLINK)].

Then, during the delayed symlink phase:

1. a is created as a symlink to e.g. .git/hooks.
2. When processing a/post-checkout, the a prefix is reused from the just-processed leaf entry without re-running the intermediate-directory check, after which…
3. symlink(target, "<wt>/a/post-checkout") resolves through the just-created symlink to write .git/hooks/post-checkout.

Although this example uses .git/hooks for simplicity, there's no actual requirement to write within the repo checkout. This can be fairly easily chained into code execution by writing to something that is known to be executed — for example, by writing to .git/hooks/post-checkout if the attacker knows that a hook-aware Git implementation will be used later, or by writing to something like ~/.local/bin.

PoC

Attached is build-bad-repo.sh, which builds a repo with the aforementioned tree structure. Cloning it with gix will set up the malicious .git/hooks/post-checkout, at which point anything that normally invokes the post-checkout hook will result in its execution, such as git checkout -b new-branch.

Impact

Arbitrary symlink creation into any existing directory the user can write to.

Disclosure

This vulnerability was found by AI (specifically, Claude Mythos) as part of Project Glasswing. This advisory was written and verified by a human.

Summary

During checkout, gitoxide does not verify that paths point to locations in the working tree. A specially crafted repository can, when cloned, place new files anywhere writable by the application.

Details

Although gix-worktree-state checks for collisions with existing files, it does not itself check if a path is really in the working tree when performing a checkout, nor do the path checks in gix-fs and gix-worktree prevent this. Cloning an untrusted repository containing specially crafted tree or blob names will create new files outside the repository, or inside the repository or a submodule's .git directory. The simplest cases are:

• A tree named .. to traverse upward. This facilitates arbitrary code execution because files can be placed in one or more locations where they are likely to be executed soon.
• A tree named .git to enter a .git directory. This facilitates arbitrary code execution because hooks can be installed.

A number of alternatives that achieve the same effect are also possible, some of which correspond to specific vulnerabilities that have affected Git in the past:

• A tree or blob whose name contains one or more /, to traverse upward or downward. For example, even without containing any tree named .. or .git, a repository can represent a file named ../outside or .git/hooks/pre-commit. This is distinct from the more intuitive case a repository containing trees that represent those paths.
• In Windows, a tree or blob whose name contains one or more \, to traverse upward or downward. (Unlike /, these are valid on other systems.) See GHSA-xjx4-8694-q2fq.
• On a case-insensitive filesystem (such as NTFS, APFS, or HFS+), a tree named as a case variant of .git.
• On HFS+, a tree named like .git or a case variant, with characters added that HFS+ ignores in collation. See https://github.com/git/git/commit/6162a1d323d24fd8cbbb1a6145a91fb849b2568f.
• On NTFS, a tree equivalent to .git (or a case variant) by the use of NTFS stream notation, such as .git::$INDEX_ALLOCATION. See GHSA-5wph-8frv-58vj.
• On an NTFS volume with 8.3 aliasing enabled, a tree named as git~1 (or a case variant). See GHSA-589j-mmg9-733v.

When a checkout creates some files outside the repository directory but fails to complete, the repository directory is usually removed, but the outside files remain.

PoC

For simplicity, these examples stage a stand-in file with a valid name, modify the index, and commit. The instructions assume sed supports -i, which is the case on most systems. If using Windows, a Git Bash shell should be used.

Example: Downward traversal to install hooks

1. Create a new repository with git init dangerous-repo-installs-hook and cd into the directory.
2. Create the stand-in called .git@hooks@pre-commit, with the contents:

   #!/bin/sh
   printf 'Vulnerable!\n'
   date >vulnerable
   

3. Stage the stand-in: git add --chmod=+x .git@hooks@pre-commit
4. Edit the index: env LC_ALL=C sed -i.orig 's|\.git@hooks@pre-commit|.git/hooks/pre-commit|' .git/index
5. Commit: git commit -m 'Initial commit'
6. Optionally, push to a private remote.

Then, on another or the same machine:

1. Clone the repository with a gix clone … command.
2. Enter the newly created directory.
3. Optionally run ls -l .git/hooks to observe that the pre-commit hook is already present.
4. Make a new file and commit it with git. This causes the payload surreptitiously installed as a pre-commit hook to run, printing the message Vulnerable! and creating a file in the current directory containing the current date and time.

Note that the effect is not limited to modifying the current directory. The payload could be written to perform any action that the user who runs git commit is capable of.

Example: Upward traversal to create a file above the working tree

1. Create a new repository with git init dangerous-repo-reaches-up, and cd into the directory.
2. Create the stand-in: echo 'A file outside the working tree, somehow.' >..@outside
3. Stage the stand-in: git add ..@outside
4. Edit the index: env LC_ALL=C sed -i.orig 's|\.\.@outside|../outside|' .git/index
5. Commit: git commit -m 'Initial commit'
6. Optionally, push to a private remote.

Then, as above, on the same or another machine, clone the repository with a gix clone … command. Observe that a file named outside is present alongside (not inside) the cloned directory.

Impact

Any use of gix or another application that makes use of gix-worktree-state, or otherwise relies on gix-fs and gix-worktree for validation, is affected, if used to clone untrusted repositories. The above description focuses on code execution, as that leads to a complete loss of confidentiality, integrity, and availability, but creating files outside a working tree without attempting to execute code can directly impact integrity as well.

In use cases where no untrusted repository is ever cloned, this vulnerability has no impact. Furthermore, the impact of this vulnerability may be lower when gix is used to clone a repository for CI/CD purposes, even if untrusted, since in such uses the environment is usually isolated and arbitrary code is usually run deliberately from the repository with necessary safeguards in place.

Summary

A malicious tree can be constructed that will, when checked out with gitoxide, permit writing an attacker-controlled symlink into any existing directory the user has write access to.

Details

During checkout, all symlink index entries are deferred and created after regular files using a single shared gix_worktree::Stack. Internally, this uses a gix_fs::Stack.

gix_fs::Stack::make_relative_path_current() caches validated path prefixes: when the previously-processed leaf component exactly matches the leading component(s) of the next path, the leaf-to-directory transition at gix-fs/src/stack.rs:195-197 invokes only delegate.push_directory(), never delegate.push().

In gix_worktree::stack::delegate::StackDelegate, when the state member is State::CreateDirectoryAndAttributesStack, Attributes::push_directory() only loads attributes (from the ODB, in the clone case), and does not perform any other checks. The on-disk symlink_metadata() check and unlink-on-collision live in StackDelegate::push()'s invocation of create_leading_directory(), which is therefore bypassed for the cached prefix. The final symlink is created with plain std::os::unix::fs::symlink, which follows symlinks in parent directories.

Therefore, it's possible to provide a tree with duplicate symlink and directory entries that exploits this. If a tree is constructed with:

1. A 120000 (symlink) entry a that points to .git/hooks.
2. A 040000 (directory) entry a with a subtree that contains a symlink from post-checkout to ../../payload.
3. A 100755 (executable file) entry payload.

This is converted by gix_index::State::from_tree() into index entries ["a" (SYMLINK), "a/post-checkout" (SYMLINK)].

Then, during the delayed symlink phase:

1. a is created as a symlink to e.g. .git/hooks.
2. When processing a/post-checkout, the a prefix is reused from the just-processed leaf entry without re-running the intermediate-directory check, after which…
3. symlink(target, "<wt>/a/post-checkout") resolves through the just-created symlink to write .git/hooks/post-checkout.

Although this example uses .git/hooks for simplicity, there's no actual requirement to write within the repo checkout. This can be fairly easily chained into code execution by writing to something that is known to be executed — for example, by writing to .git/hooks/post-checkout if the attacker knows that a hook-aware Git implementation will be used later, or by writing to something like ~/.local/bin.

PoC

Attached is build-bad-repo.sh, which builds a repo with the aforementioned tree structure. Cloning it with gix will set up the malicious .git/hooks/post-checkout, at which point anything that normally invokes the post-checkout hook will result in its execution, such as git checkout -b new-branch.

Impact

Arbitrary symlink creation into any existing directory the user can write to.

Disclosure

This vulnerability was found by AI (specifically, Claude Mythos) as part of Project Glasswing. This advisory was written and verified by a human.

Summary

During checkout, gitoxide does not verify that paths point to locations in the working tree. A specially crafted repository can, when cloned, place new files anywhere writable by the application.

Details

Although gix-worktree-state checks for collisions with existing files, it does not itself check if a path is really in the working tree when performing a checkout, nor do the path checks in gix-fs and gix-worktree prevent this. Cloning an untrusted repository containing specially crafted tree or blob names will create new files outside the repository, or inside the repository or a submodule's .git directory. The simplest cases are:

• A tree named .. to traverse upward. This facilitates arbitrary code execution because files can be placed in one or more locations where they are likely to be executed soon.
• A tree named .git to enter a .git directory. This facilitates arbitrary code execution because hooks can be installed.

A number of alternatives that achieve the same effect are also possible, some of which correspond to specific vulnerabilities that have affected Git in the past:

• A tree or blob whose name contains one or more /, to traverse upward or downward. For example, even without containing any tree named .. or .git, a repository can represent a file named ../outside or .git/hooks/pre-commit. This is distinct from the more intuitive case a repository containing trees that represent those paths.
• In Windows, a tree or blob whose name contains one or more \, to traverse upward or downward. (Unlike /, these are valid on other systems.) See GHSA-xjx4-8694-q2fq.
• On a case-insensitive filesystem (such as NTFS, APFS, or HFS+), a tree named as a case variant of .git.
• On HFS+, a tree named like .git or a case variant, with characters added that HFS+ ignores in collation. See https://github.com/git/git/commit/6162a1d323d24fd8cbbb1a6145a91fb849b2568f.
• On NTFS, a tree equivalent to .git (or a case variant) by the use of NTFS stream notation, such as .git::$INDEX_ALLOCATION. See GHSA-5wph-8frv-58vj.
• On an NTFS volume with 8.3 aliasing enabled, a tree named as git~1 (or a case variant). See GHSA-589j-mmg9-733v.

When a checkout creates some files outside the repository directory but fails to complete, the repository directory is usually removed, but the outside files remain.

PoC

For simplicity, these examples stage a stand-in file with a valid name, modify the index, and commit. The instructions assume sed supports -i, which is the case on most systems. If using Windows, a Git Bash shell should be used.

Example: Downward traversal to install hooks

1. Create a new repository with git init dangerous-repo-installs-hook and cd into the directory.
2. Create the stand-in called .git@hooks@pre-commit, with the contents:

   #!/bin/sh
   printf 'Vulnerable!\n'
   date >vulnerable
   

3. Stage the stand-in: git add --chmod=+x .git@hooks@pre-commit
4. Edit the index: env LC_ALL=C sed -i.orig 's|\.git@hooks@pre-commit|.git/hooks/pre-commit|' .git/index
5. Commit: git commit -m 'Initial commit'
6. Optionally, push to a private remote.

Then, on another or the same machine:

1. Clone the repository with a gix clone … command.
2. Enter the newly created directory.
3. Optionally run ls -l .git/hooks to observe that the pre-commit hook is already present.
4. Make a new file and commit it with git. This causes the payload surreptitiously installed as a pre-commit hook to run, printing the message Vulnerable! and creating a file in the current directory containing the current date and time.

Note that the effect is not limited to modifying the current directory. The payload could be written to perform any action that the user who runs git commit is capable of.

Example: Upward traversal to create a file above the working tree

1. Create a new repository with git init dangerous-repo-reaches-up, and cd into the directory.
2. Create the stand-in: echo 'A file outside the working tree, somehow.' >..@outside
3. Stage the stand-in: git add ..@outside
4. Edit the index: env LC_ALL=C sed -i.orig 's|\.\.@outside|../outside|' .git/index
5. Commit: git commit -m 'Initial commit'
6. Optionally, push to a private remote.

Then, as above, on the same or another machine, clone the repository with a gix clone … command. Observe that a file named outside is present alongside (not inside) the cloned directory.

Impact

Any use of gix or another application that makes use of gix-worktree-state, or otherwise relies on gix-fs and gix-worktree for validation, is affected, if used to clone untrusted repositories. The above description focuses on code execution, as that leads to a complete loss of confidentiality, integrity, and availability, but creating files outside a working tree without attempting to execute code can directly impact integrity as well.

In use cases where no untrusted repository is ever cloned, this vulnerability has no impact. Furthermore, the impact of this vulnerability may be lower when gix is used to clone a repository for CI/CD purposes, even if untrusted, since in such uses the environment is usually isolated and arbitrary code is usually run deliberately from the repository with necessary safeguards in place.

Summary

A malicious tree can be constructed that will, when checked out with gitoxide, permit writing an attacker-controlled symlink into any existing directory the user has write access to.

Details

During checkout, all symlink index entries are deferred and created after regular files using a single shared gix_worktree::Stack. Internally, this uses a gix_fs::Stack.

gix_fs::Stack::make_relative_path_current() caches validated path prefixes: when the previously-processed leaf component exactly matches the leading component(s) of the next path, the leaf-to-directory transition at gix-fs/src/stack.rs:195-197 invokes only delegate.push_directory(), never delegate.push().

In gix_worktree::stack::delegate::StackDelegate, when the state member is State::CreateDirectoryAndAttributesStack, Attributes::push_directory() only loads attributes (from the ODB, in the clone case), and does not perform any other checks. The on-disk symlink_metadata() check and unlink-on-collision live in StackDelegate::push()'s invocation of create_leading_directory(), which is therefore bypassed for the cached prefix. The final symlink is created with plain std::os::unix::fs::symlink, which follows symlinks in parent directories.

Therefore, it's possible to provide a tree with duplicate symlink and directory entries that exploits this. If a tree is constructed with:

1. A 120000 (symlink) entry a that points to .git/hooks.
2. A 040000 (directory) entry a with a subtree that contains a symlink from post-checkout to ../../payload.
3. A 100755 (executable file) entry payload.

This is converted by gix_index::State::from_tree() into index entries ["a" (SYMLINK), "a/post-checkout" (SYMLINK)].

Then, during the delayed symlink phase:

1. a is created as a symlink to e.g. .git/hooks.
2. When processing a/post-checkout, the a prefix is reused from the just-processed leaf entry without re-running the intermediate-directory check, after which…
3. symlink(target, "<wt>/a/post-checkout") resolves through the just-created symlink to write .git/hooks/post-checkout.

Although this example uses .git/hooks for simplicity, there's no actual requirement to write within the repo checkout. This can be fairly easily chained into code execution by writing to something that is known to be executed — for example, by writing to .git/hooks/post-checkout if the attacker knows that a hook-aware Git implementation will be used later, or by writing to something like ~/.local/bin.

PoC

Attached is build-bad-repo.sh, which builds a repo with the aforementioned tree structure. Cloning it with gix will set up the malicious .git/hooks/post-checkout, at which point anything that normally invokes the post-checkout hook will result in its execution, such as git checkout -b new-branch.

Impact

Arbitrary symlink creation into any existing directory the user can write to.

Disclosure

This vulnerability was found by AI (specifically, Claude Mythos) as part of Project Glasswing. This advisory was written and verified by a human.

Summary

During checkout, gitoxide does not verify that paths point to locations in the working tree. A specially crafted repository can, when cloned, place new files anywhere writable by the application.

Details

Although gix-worktree-state checks for collisions with existing files, it does not itself check if a path is really in the working tree when performing a checkout, nor do the path checks in gix-fs and gix-worktree prevent this. Cloning an untrusted repository containing specially crafted tree or blob names will create new files outside the repository, or inside the repository or a submodule's .git directory. The simplest cases are:

• A tree named .. to traverse upward. This facilitates arbitrary code execution because files can be placed in one or more locations where they are likely to be executed soon.
• A tree named .git to enter a .git directory. This facilitates arbitrary code execution because hooks can be installed.

A number of alternatives that achieve the same effect are also possible, some of which correspond to specific vulnerabilities that have affected Git in the past:

• A tree or blob whose name contains one or more /, to traverse upward or downward. For example, even without containing any tree named .. or .git, a repository can represent a file named ../outside or .git/hooks/pre-commit. This is distinct from the more intuitive case a repository containing trees that represent those paths.
• In Windows, a tree or blob whose name contains one or more \, to traverse upward or downward. (Unlike /, these are valid on other systems.) See GHSA-xjx4-8694-q2fq.
• On a case-insensitive filesystem (such as NTFS, APFS, or HFS+), a tree named as a case variant of .git.
• On HFS+, a tree named like .git or a case variant, with characters added that HFS+ ignores in collation. See https://github.com/git/git/commit/6162a1d323d24fd8cbbb1a6145a91fb849b2568f.
• On NTFS, a tree equivalent to .git (or a case variant) by the use of NTFS stream notation, such as .git::$INDEX_ALLOCATION. See GHSA-5wph-8frv-58vj.
• On an NTFS volume with 8.3 aliasing enabled, a tree named as git~1 (or a case variant). See GHSA-589j-mmg9-733v.

When a checkout creates some files outside the repository directory but fails to complete, the repository directory is usually removed, but the outside files remain.

PoC

For simplicity, these examples stage a stand-in file with a valid name, modify the index, and commit. The instructions assume sed supports -i, which is the case on most systems. If using Windows, a Git Bash shell should be used.

Example: Downward traversal to install hooks

1. Create a new repository with git init dangerous-repo-installs-hook and cd into the directory.
2. Create the stand-in called .git@hooks@pre-commit, with the contents:

   #!/bin/sh
   printf 'Vulnerable!\n'
   date >vulnerable
   

3. Stage the stand-in: git add --chmod=+x .git@hooks@pre-commit
4. Edit the index: env LC_ALL=C sed -i.orig 's|\.git@hooks@pre-commit|.git/hooks/pre-commit|' .git/index
5. Commit: git commit -m 'Initial commit'
6. Optionally, push to a private remote.

Then, on another or the same machine:

1. Clone the repository with a gix clone … command.
2. Enter the newly created directory.
3. Optionally run ls -l .git/hooks to observe that the pre-commit hook is already present.
4. Make a new file and commit it with git. This causes the payload surreptitiously installed as a pre-commit hook to run, printing the message Vulnerable! and creating a file in the current directory containing the current date and time.

Note that the effect is not limited to modifying the current directory. The payload could be written to perform any action that the user who runs git commit is capable of.

Example: Upward traversal to create a file above the working tree

1. Create a new repository with git init dangerous-repo-reaches-up, and cd into the directory.
2. Create the stand-in: echo 'A file outside the working tree, somehow.' >..@outside
3. Stage the stand-in: git add ..@outside
4. Edit the index: env LC_ALL=C sed -i.orig 's|\.\.@outside|../outside|' .git/index
5. Commit: git commit -m 'Initial commit'
6. Optionally, push to a private remote.