activestorage

Impact

In its default configuration, a Rails application that displays image variants may allow an unauthenticated attacker to read arbitrary files from the server, including the process environment. That environment typically holds secret_key_base and often credentials for external systems, which may in turn allow escalation to remote code execution or lateral movement to those systems.

Details

libvips reads and writes file formats through "loaders" and "savers" (or more generally "operations"), many of which are backed by third-party libraries. It marks some of these operations as "unfuzzed", meaning they are unsafe for untrusted content, and several handle formats unrelated to web images. Active Storage did not disable the unfuzzed operations, so an attacker who can upload a crafted file and cause a variant to be generated from it may be able to invoke one.

We are aware of a mechanism by which an attacker, by uploading a crafted file, is able to cause disclosure of the contents of arbitrary files accessible on the filesystem of the targeted application. One specific attack chain has been reported to us (see "Disclosure" below), but we do not assume it is the only one that exists.

Affected applications

An application is affected if it meets all of these requirements:

• Uses libvips for Active Storage image processing. This is config.active_storage.variant_processor = :vips, which load_defaults 7.0 set and no later default has changed.
• Allows image uploads from untrusted users.

Generating variants is not a separate requirement.

Mitigation

• Upgrade to a fixed version of activestorage.
• The minimum version of libvips must be upgraded to >= 8.13.
• Change secret_key_base and change any secrets accessible in the application environment (see "Expire and change secrets" below)

Earlier versions of libvips (< 8.13) cannot disable unfuzzed operations at all, and Active Storage will raise an exception during boot in such an unsecurable environment.

Expire and change secrets

Upgrading closes the vulnerability but does not undo an exfiltrated secret if that already occurred. An affected application should treat every secret readable by the application process as potentially exposed and change it, including:

• secret_key_base
• The master key, whether stored in config/master.key or supplied as RAILS_MASTER_KEY, along with everything in config/credentials.yml.enc that it decrypts
• Credentials for the Active Storage service, such as S3, GCS, or Azure keys
• Database credentials
• Tokens and keys for any third-party service the application calls

Changing secret_key_base expires active sessions and requires users to log in again. Encrypted cookies, signed cookies, signed global IDs, and Active Storage URLs are also affected.

Rotation should only be used as an intermediate step if necessary. Do not retain an exposed secret as a fallback.

Workarounds

If libvips < 8.13 is being used, there are no workarounds available other than removing the dependency on libvips from the application. Some applications may have ruby-vips declared as a dependency only for image analysis, and those applications may be able to simply remove ruby-vips from the Gemfile to remove libvips from the application. Applications that do not use Active Storage can remove ruby-vips from the Gemfile to avoid the boot-time checks.

If libvips >= 8.13 is present on the system, applications can disable the unfuzzed operations without upgrading Rails by setting the VIPS_BLOCK_UNTRUSTED environment variable, which libvips reads while initializing.

Applications also running ruby-vips >= 2.2.1 or later can instead call Vips.block_untrusted(true) from an initializer.

Releases

The fixed releases are available at the normal locations.

Versions affected

• activestorage < 7.2.3.2
• activestorage >= 8.0, < 8.0.5.1
• activestorage >= 8.1, < 8.1.3.1

Disclosure

Technical details of the attack chain are intentionally omitted from this advisory. They would add nothing to an administrator's decision to upgrade, while making it substantially easier to attack applications that have not yet done so.

Details will be disclosed no later than 2026-08-28, via the Rails Security Announcements forum.

Credit

This issue was responsibly reported by 0xacb, s3np41k1r1t0 and castilho from Ethiack, and RyotaK from GMO Flatt Security Inc..

References

• libvips 8.13 release notes, blocking of unfuzzed loaders
• W.A. Arbaugh, W.L. Fithen, and J. McHugh, "Windows of Vulnerability: A Case Study Analysis", IEEE Computer 33(12), December 2000
• https://ethiack.com/info-hub/research/kindarails2shell-rails-rce-cve
• https://blog.flatt.tech/entry/kindarails2shell_rails

Impact

In its default configuration, a Rails application that displays image variants may allow an unauthenticated attacker to read arbitrary files from the server, including the process environment. That environment typically holds secret_key_base and often credentials for external systems, which may in turn allow escalation to remote code execution or lateral movement to those systems.

Details

libvips reads and writes file formats through "loaders" and "savers" (or more generally "operations"), many of which are backed by third-party libraries. It marks some of these operations as "unfuzzed", meaning they are unsafe for untrusted content, and several handle formats unrelated to web images. Active Storage did not disable the unfuzzed operations, so an attacker who can upload a crafted file and cause a variant to be generated from it may be able to invoke one.

We are aware of a mechanism by which an attacker, by uploading a crafted file, is able to cause disclosure of the contents of arbitrary files accessible on the filesystem of the targeted application. One specific attack chain has been reported to us (see "Disclosure" below), but we do not assume it is the only one that exists.

Affected applications

An application is affected if it meets all of these requirements:

• Uses libvips for Active Storage image processing. This is config.active_storage.variant_processor = :vips, which load_defaults 7.0 set and no later default has changed.
• Allows image uploads from untrusted users.

Generating variants is not a separate requirement.

Mitigation

• Upgrade to a fixed version of activestorage.
• The minimum version of libvips must be upgraded to >= 8.13.
• Change secret_key_base and change any secrets accessible in the application environment (see "Expire and change secrets" below)

Earlier versions of libvips (< 8.13) cannot disable unfuzzed operations at all, and Active Storage will raise an exception during boot in such an unsecurable environment.

Expire and change secrets

Upgrading closes the vulnerability but does not undo an exfiltrated secret if that already occurred. An affected application should treat every secret readable by the application process as potentially exposed and change it, including:

• secret_key_base
• The master key, whether stored in config/master.key or supplied as RAILS_MASTER_KEY, along with everything in config/credentials.yml.enc that it decrypts
• Credentials for the Active Storage service, such as S3, GCS, or Azure keys
• Database credentials
• Tokens and keys for any third-party service the application calls

Changing secret_key_base expires active sessions and requires users to log in again. Encrypted cookies, signed cookies, signed global IDs, and Active Storage URLs are also affected.

Rotation should only be used as an intermediate step if necessary. Do not retain an exposed secret as a fallback.

Workarounds

If libvips < 8.13 is being used, there are no workarounds available other than removing the dependency on libvips from the application. Some applications may have ruby-vips declared as a dependency only for image analysis, and those applications may be able to simply remove ruby-vips from the Gemfile to remove libvips from the application. Applications that do not use Active Storage can remove ruby-vips from the Gemfile to avoid the boot-time checks.

If libvips >= 8.13 is present on the system, applications can disable the unfuzzed operations without upgrading Rails by setting the VIPS_BLOCK_UNTRUSTED environment variable, which libvips reads while initializing.

Applications also running ruby-vips >= 2.2.1 or later can instead call Vips.block_untrusted(true) from an initializer.

Releases

The fixed releases are available at the normal locations.

Versions affected

• activestorage < 7.2.3.2
• activestorage >= 8.0, < 8.0.5.1
• activestorage >= 8.1, < 8.1.3.1

Disclosure

Technical details of the attack chain are intentionally omitted from this advisory. They would add nothing to an administrator's decision to upgrade, while making it substantially easier to attack applications that have not yet done so.

Details will be disclosed no later than 2026-08-28, via the Rails Security Announcements forum.

Credit

This issue was responsibly reported by 0xacb, s3np41k1r1t0 and castilho from Ethiack, and RyotaK from GMO Flatt Security Inc..

References

• libvips 8.13 release notes, blocking of unfuzzed loaders
• W.A. Arbaugh, W.L. Fithen, and J. McHugh, "Windows of Vulnerability: A Case Study Analysis", IEEE Computer 33(12), December 2000
• https://ethiack.com/info-hub/research/kindarails2shell-rails-rce-cve
• https://blog.flatt.tech/entry/kindarails2shell_rails

Impact

In its default configuration, a Rails application that displays image variants may allow an unauthenticated attacker to read arbitrary files from the server, including the process environment. That environment typically holds secret_key_base and often credentials for external systems, which may in turn allow escalation to remote code execution or lateral movement to those systems.

Details

libvips reads and writes file formats through "loaders" and "savers" (or more generally "operations"), many of which are backed by third-party libraries. It marks some of these operations as "unfuzzed", meaning they are unsafe for untrusted content, and several handle formats unrelated to web images. Active Storage did not disable the unfuzzed operations, so an attacker who can upload a crafted file and cause a variant to be generated from it may be able to invoke one.

We are aware of a mechanism by which an attacker, by uploading a crafted file, is able to cause disclosure of the contents of arbitrary files accessible on the filesystem of the targeted application. One specific attack chain has been reported to us (see "Disclosure" below), but we do not assume it is the only one that exists.

Affected applications

An application is affected if it meets all of these requirements:

• Uses libvips for Active Storage image processing. This is config.active_storage.variant_processor = :vips, which load_defaults 7.0 set and no later default has changed.
• Allows image uploads from untrusted users.

Generating variants is not a separate requirement.

Mitigation

• Upgrade to a fixed version of activestorage.
• The minimum version of libvips must be upgraded to >= 8.13.
• Change secret_key_base and change any secrets accessible in the application environment (see "Expire and change secrets" below)

Earlier versions of libvips (< 8.13) cannot disable unfuzzed operations at all, and Active Storage will raise an exception during boot in such an unsecurable environment.

Expire and change secrets

Upgrading closes the vulnerability but does not undo an exfiltrated secret if that already occurred. An affected application should treat every secret readable by the application process as potentially exposed and change it, including:

• secret_key_base
• The master key, whether stored in config/master.key or supplied as RAILS_MASTER_KEY, along with everything in config/credentials.yml.enc that it decrypts
• Credentials for the Active Storage service, such as S3, GCS, or Azure keys
• Database credentials
• Tokens and keys for any third-party service the application calls

Changing secret_key_base expires active sessions and requires users to log in again. Encrypted cookies, signed cookies, signed global IDs, and Active Storage URLs are also affected.

Rotation should only be used as an intermediate step if necessary. Do not retain an exposed secret as a fallback.

Workarounds

If libvips < 8.13 is being used, there are no workarounds available other than removing the dependency on libvips from the application. Some applications may have ruby-vips declared as a dependency only for image analysis, and those applications may be able to simply remove ruby-vips from the Gemfile to remove libvips from the application. Applications that do not use Active Storage can remove ruby-vips from the Gemfile to avoid the boot-time checks.

If libvips >= 8.13 is present on the system, applications can disable the unfuzzed operations without upgrading Rails by setting the VIPS_BLOCK_UNTRUSTED environment variable, which libvips reads while initializing.

Applications also running ruby-vips >= 2.2.1 or later can instead call Vips.block_untrusted(true) from an initializer.

Releases

The fixed releases are available at the normal locations.

Versions affected

• activestorage < 7.2.3.2
• activestorage >= 8.0, < 8.0.5.1
• activestorage >= 8.1, < 8.1.3.1

Disclosure

Technical details of the attack chain are intentionally omitted from this advisory. They would add nothing to an administrator's decision to upgrade, while making it substantially easier to attack applications that have not yet done so.

Details will be disclosed no later than 2026-08-28, via the Rails Security Announcements forum.

Credit

This issue was responsibly reported by 0xacb, s3np41k1r1t0 and castilho from Ethiack, and RyotaK from GMO Flatt Security Inc..

References

• libvips 8.13 release notes, blocking of unfuzzed loaders
• W.A. Arbaugh, W.L. Fithen, and J. McHugh, "Windows of Vulnerability: A Case Study Analysis", IEEE Computer 33(12), December 2000
• https://ethiack.com/info-hub/research/kindarails2shell-rails-rce-cve
• https://blog.flatt.tech/entry/kindarails2shell_rails

Impact

In its default configuration, a Rails application that displays image variants may allow an unauthenticated attacker to read arbitrary files from the server, including the process environment. That environment typically holds secret_key_base and often credentials for external systems, which may in turn allow escalation to remote code execution or lateral movement to those systems.

Details

libvips reads and writes file formats through "loaders" and "savers" (or more generally "operations"), many of which are backed by third-party libraries. It marks some of these operations as "unfuzzed", meaning they are unsafe for untrusted content, and several handle formats unrelated to web images. Active Storage did not disable the unfuzzed operations, so an attacker who can upload a crafted file and cause a variant to be generated from it may be able to invoke one.

We are aware of a mechanism by which an attacker, by uploading a crafted file, is able to cause disclosure of the contents of arbitrary files accessible on the filesystem of the targeted application. One specific attack chain has been reported to us (see "Disclosure" below), but we do not assume it is the only one that exists.

Affected applications

An application is affected if it meets all of these requirements:

• Uses libvips for Active Storage image processing. This is config.active_storage.variant_processor = :vips, which load_defaults 7.0 set and no later default has changed.
• Allows image uploads from untrusted users.

Generating variants is not a separate requirement.

Mitigation

• Upgrade to a fixed version of activestorage.
• The minimum version of libvips must be upgraded to >= 8.13.
• Change secret_key_base and change any secrets accessible in the application environment (see "Expire and change secrets" below)

Earlier versions of libvips (< 8.13) cannot disable unfuzzed operations at all, and Active Storage will raise an exception during boot in such an unsecurable environment.

Expire and change secrets

Upgrading closes the vulnerability but does not undo an exfiltrated secret if that already occurred. An affected application should treat every secret readable by the application process as potentially exposed and change it, including:

• secret_key_base
• The master key, whether stored in config/master.key or supplied as RAILS_MASTER_KEY, along with everything in config/credentials.yml.enc that it decrypts
• Credentials for the Active Storage service, such as S3, GCS, or Azure keys
• Database credentials
• Tokens and keys for any third-party service the application calls

Changing secret_key_base expires active sessions and requires users to log in again. Encrypted cookies, signed cookies, signed global IDs, and Active Storage URLs are also affected.

Rotation should only be used as an intermediate step if necessary. Do not retain an exposed secret as a fallback.

Workarounds

If libvips < 8.13 is being used, there are no workarounds available other than removing the dependency on libvips from the application. Some applications may have ruby-vips declared as a dependency only for image analysis, and those applications may be able to simply remove ruby-vips from the Gemfile to remove libvips from the application. Applications that do not use Active Storage can remove ruby-vips from the Gemfile to avoid the boot-time checks.

If libvips >= 8.13 is present on the system, applications can disable the unfuzzed operations without upgrading Rails by setting the VIPS_BLOCK_UNTRUSTED environment variable, which libvips reads while initializing.

Applications also running ruby-vips >= 2.2.1 or later can instead call Vips.block_untrusted(true) from an initializer.

Releases

The fixed releases are available at the normal locations.

Versions affected

• activestorage < 7.2.3.2
• activestorage >= 8.0, < 8.0.5.1
• activestorage >= 8.1, < 8.1.3.1

Disclosure

Technical details of the attack chain are intentionally omitted from this advisory. They would add nothing to an administrator's decision to upgrade, while making it substantially easier to attack applications that have not yet done so.

Details will be disclosed no later than 2026-08-28, via the Rails Security Announcements forum.

Credit

This issue was responsibly reported by 0xacb, s3np41k1r1t0 and castilho from Ethiack, and RyotaK from GMO Flatt Security Inc..

References

• libvips 8.13 release notes, blocking of unfuzzed loaders
• W.A. Arbaugh, W.L. Fithen, and J. McHugh, "Windows of Vulnerability: A Case Study Analysis", IEEE Computer 33(12), December 2000
• https://ethiack.com/info-hub/research/kindarails2shell-rails-rce-cve
• https://blog.flatt.tech/entry/kindarails2shell_rails

Impact

In its default configuration, a Rails application that displays image variants may allow an unauthenticated attacker to read arbitrary files from the server, including the process environment. That environment typically holds secret_key_base and often credentials for external systems, which may in turn allow escalation to remote code execution or lateral movement to those systems.

Details

libvips reads and writes file formats through "loaders" and "savers" (or more generally "operations"), many of which are backed by third-party libraries. It marks some of these operations as "unfuzzed", meaning they are unsafe for untrusted content, and several handle formats unrelated to web images. Active Storage did not disable the unfuzzed operations, so an attacker who can upload a crafted file and cause a variant to be generated from it may be able to invoke one.

We are aware of a mechanism by which an attacker, by uploading a crafted file, is able to cause disclosure of the contents of arbitrary files accessible on the filesystem of the targeted application. One specific attack chain has been reported to us (see "Disclosure" below), but we do not assume it is the only one that exists.

Affected applications

An application is affected if it meets all of these requirements:

• Uses libvips for Active Storage image processing. This is config.active_storage.variant_processor = :vips, which load_defaults 7.0 set and no later default has changed.
• Allows image uploads from untrusted users.

Generating variants is not a separate requirement.

Mitigation

• Upgrade to a fixed version of activestorage.
• The minimum version of libvips must be upgraded to >= 8.13.
• Change secret_key_base and change any secrets accessible in the application environment (see "Expire and change secrets" below)

Earlier versions of libvips (< 8.13) cannot disable unfuzzed operations at all, and Active Storage will raise an exception during boot in such an unsecurable environment.

Expire and change secrets

Upgrading closes the vulnerability but does not undo an exfiltrated secret if that already occurred. An affected application should treat every secret readable by the application process as potentially exposed and change it, including:

• secret_key_base
• The master key, whether stored in config/master.key or supplied as RAILS_MASTER_KEY, along with everything in config/credentials.yml.enc that it decrypts
• Credentials for the Active Storage service, such as S3, GCS, or Azure keys
• Database credentials
• Tokens and keys for any third-party service the application calls

Changing secret_key_base expires active sessions and requires users to log in again. Encrypted cookies, signed cookies, signed global IDs, and Active Storage URLs are also affected.

Rotation should only be used as an intermediate step if necessary. Do not retain an exposed secret as a fallback.

Workarounds

If libvips < 8.13 is being used, there are no workarounds available other than removing the dependency on libvips from the application. Some applications may have ruby-vips declared as a dependency only for image analysis, and those applications may be able to simply remove ruby-vips from the Gemfile to remove libvips from the application. Applications that do not use Active Storage can remove ruby-vips from the Gemfile to avoid the boot-time checks.

If libvips >= 8.13 is present on the system, applications can disable the unfuzzed operations without upgrading Rails by setting the VIPS_BLOCK_UNTRUSTED environment variable, which libvips reads while initializing.

Applications also running ruby-vips >= 2.2.1 or later can instead call Vips.block_untrusted(true) from an initializer.

Releases

The fixed releases are available at the normal locations.

Versions affected

• activestorage < 7.2.3.2
• activestorage >= 8.0, < 8.0.5.1
• activestorage >= 8.1, < 8.1.3.1

Disclosure

Technical details of the attack chain are intentionally omitted from this advisory. They would add nothing to an administrator's decision to upgrade, while making it substantially easier to attack applications that have not yet done so.

Details will be disclosed no later than 2026-08-28, via the Rails Security Announcements forum.

Credit

This issue was responsibly reported by 0xacb, s3np41k1r1t0 and castilho from Ethiack, and RyotaK from GMO Flatt Security Inc..

References

• libvips 8.13 release notes, blocking of unfuzzed loaders
• W.A. Arbaugh, W.L. Fithen, and J. McHugh, "Windows of Vulnerability: A Case Study Analysis", IEEE Computer 33(12), December 2000
• https://ethiack.com/info-hub/research/kindarails2shell-rails-rce-cve
• https://blog.flatt.tech/entry/kindarails2shell_rails

Impact

In its default configuration, a Rails application that displays image variants may allow an unauthenticated attacker to read arbitrary files from the server, including the process environment. That environment typically holds secret_key_base and often credentials for external systems, which may in turn allow escalation to remote code execution or lateral movement to those systems.

Details

libvips reads and writes file formats through "loaders" and "savers" (or more generally "operations"), many of which are backed by third-party libraries. It marks some of these operations as "unfuzzed", meaning they are unsafe for untrusted content, and several handle formats unrelated to web images. Active Storage did not disable the unfuzzed operations, so an attacker who can upload a crafted file and cause a variant to be generated from it may be able to invoke one.

We are aware of a mechanism by which an attacker, by uploading a crafted file, is able to cause disclosure of the contents of arbitrary files accessible on the filesystem of the targeted application. One specific attack chain has been reported to us (see "Disclosure" below), but we do not assume it is the only one that exists.

Affected applications

An application is affected if it meets all of these requirements:

• Uses libvips for Active Storage image processing. This is config.active_storage.variant_processor = :vips, which load_defaults 7.0 set and no later default has changed.
• Allows image uploads from untrusted users.

Generating variants is not a separate requirement.

Mitigation

• Upgrade to a fixed version of activestorage.
• The minimum version of libvips must be upgraded to >= 8.13.
• Change secret_key_base and change any secrets accessible in the application environment (see "Expire and change secrets" below)

Earlier versions of libvips (< 8.13) cannot disable unfuzzed operations at all, and Active Storage will raise an exception during boot in such an unsecurable environment.

Expire and change secrets

Upgrading closes the vulnerability but does not undo an exfiltrated secret if that already occurred. An affected application should treat every secret readable by the application process as potentially exposed and change it, including:

• secret_key_base
• The master key, whether stored in config/master.key or supplied as RAILS_MASTER_KEY, along with everything in config/credentials.yml.enc that it decrypts
• Credentials for the Active Storage service, such as S3, GCS, or Azure keys
• Database credentials
• Tokens and keys for any third-party service the application calls

Changing secret_key_base expires active sessions and requires users to log in again. Encrypted cookies, signed cookies, signed global IDs, and Active Storage URLs are also affected.

Rotation should only be used as an intermediate step if necessary. Do not retain an exposed secret as a fallback.

Workarounds

If libvips < 8.13 is being used, there are no workarounds available other than removing the dependency on libvips from the application. Some applications may have ruby-vips declared as a dependency only for image analysis, and those applications may be able to simply remove ruby-vips from the Gemfile to remove libvips from the application. Applications that do not use Active Storage can remove ruby-vips from the Gemfile to avoid the boot-time checks.

If libvips >= 8.13 is present on the system, applications can disable the unfuzzed operations without upgrading Rails by setting the VIPS_BLOCK_UNTRUSTED environment variable, which libvips reads while initializing.

Applications also running ruby-vips >= 2.2.1 or later can instead call Vips.block_untrusted(true) from an initializer.

Releases

The fixed releases are available at the normal locations.

Versions affected

• activestorage < 7.2.3.2
• activestorage >= 8.0, < 8.0.5.1
• activestorage >= 8.1, < 8.1.3.1

Disclosure

Technical details of the attack chain are intentionally omitted from this advisory. They would add nothing to an administrator's decision to upgrade, while making it substantially easier to attack applications that have not yet done so.

Details will be disclosed no later than 2026-08-28, via the Rails Security Announcements forum.

Credit

This issue was responsibly reported by 0xacb, s3np41k1r1t0 and castilho from Ethiack, and RyotaK from GMO Flatt Security Inc..

References

• libvips 8.13 release notes, blocking of unfuzzed loaders
• W.A. Arbaugh, W.L. Fithen, and J. McHugh, "Windows of Vulnerability: A Case Study Analysis", IEEE Computer 33(12), December 2000
• https://ethiack.com/info-hub/research/kindarails2shell-rails-rce-cve
• https://blog.flatt.tech/entry/kindarails2shell_rails

Impact

Active Storage's proxy controller does not limit the number of byte ranges in an HTTP Range header. A request with thousands of small ranges causes disproportionate CPU usage compared to a normal request for the same file, possibly resulting in a DoS vulnerability.

Releases

The fixed releases are available at the normal locations.

Credit

This issue was responsibly reported by Hackerone researcher thwin_htet.

Impact

Active Storage's DiskService#delete_prefixed passes blob keys directly to Dir.glob without escaping glob metacharacters. If a blob key contains attacker-controlled input or custom-generated keys with glob metacharacters, it may be possible to delete unintended files from the storage directory.

Releases

The fixed releases are available at the normal locations.

Impact

Active Storage's DiskService#path_for does not validate that the resolved filesystem path remains within the storage root directory. If a blob key containing path traversal sequences (e.g. ../) is used, it could allow reading, writing, or deleting arbitrary files on the server. Blob keys are expected to be trusted strings, but some applications could be passing user input as keys and would be affected.

Releases

The fixed releases are available at the normal locations.

Credit

This issue was responsibly reported by Hackerone researcher ksw9722.

Impact

When serving files through Active Storage's Blobs::ProxyController, the controller loads the entire requested byte range into memory before sending it. A request with a large or unbounded Range header (e.g. bytes=0-) could cause the server to allocate memory proportional to the file size, possibly resulting in a DoS vulnerability through memory exhaustion.

Releases

The fixed releases are available at the normal locations.

Credit

This issue was responsibly reported by Hackerone user pirikara

Impact

Active Storage's DirectUploadsController accepts arbitrary metadata from the client and persists it on the blob. Because internal flags like identified and analyzed are stored in the same metadata hash, a malicious direct-upload client could set these flags.

Releases

The fixed releases are available at the normal locations.

Credit

This was responsible reported by Hackerone researcher pwnie

Impact

In its default configuration, a Rails application that displays image variants may allow an unauthenticated attacker to read arbitrary files from the server, including the process environment. That environment typically holds secret_key_base and often credentials for external systems, which may in turn allow escalation to remote code execution or lateral movement to those systems.

Details

libvips reads and writes file formats through "loaders" and "savers" (or more generally "operations"), many of which are backed by third-party libraries. It marks some of these operations as "unfuzzed", meaning they are unsafe for untrusted content, and several handle formats unrelated to web images. Active Storage did not disable the unfuzzed operations, so an attacker who can upload a crafted file and cause a variant to be generated from it may be able to invoke one.

We are aware of a mechanism by which an attacker, by uploading a crafted file, is able to cause disclosure of the contents of arbitrary files accessible on the filesystem of the targeted application. One specific attack chain has been reported to us (see "Disclosure" below), but we do not assume it is the only one that exists.

Affected applications

An application is affected if it meets all of these requirements:

• Uses libvips for Active Storage image processing. This is config.active_storage.variant_processor = :vips, which load_defaults 7.0 set and no later default has changed.
• Allows image uploads from untrusted users.

Generating variants is not a separate requirement.

Mitigation

• Upgrade to a fixed version of activestorage.
• The minimum version of libvips must be upgraded to >= 8.13.
• Change secret_key_base and change any secrets accessible in the application environment (see "Expire and change secrets" below)

Earlier versions of libvips (< 8.13) cannot disable unfuzzed operations at all, and Active Storage will raise an exception during boot in such an unsecurable environment.

Expire and change secrets

Upgrading closes the vulnerability but does not undo an exfiltrated secret if that already occurred. An affected application should treat every secret readable by the application process as potentially exposed and change it, including:

• secret_key_base
• The master key, whether stored in config/master.key or supplied as RAILS_MASTER_KEY, along with everything in config/credentials.yml.enc that it decrypts
• Credentials for the Active Storage service, such as S3, GCS, or Azure keys
• Database credentials
• Tokens and keys for any third-party service the application calls

Changing secret_key_base expires active sessions and requires users to log in again. Encrypted cookies, signed cookies, signed global IDs, and Active Storage URLs are also affected.

Rotation should only be used as an intermediate step if necessary. Do not retain an exposed secret as a fallback.

Workarounds

If libvips < 8.13 is being used, there are no workarounds available other than removing the dependency on libvips from the application. Some applications may have ruby-vips declared as a dependency only for image analysis, and those applications may be able to simply remove ruby-vips from the Gemfile to remove libvips from the application. Applications that do not use Active Storage can remove ruby-vips from the Gemfile to avoid the boot-time checks.

If libvips >= 8.13 is present on the system, applications can disable the unfuzzed operations without upgrading Rails by setting the VIPS_BLOCK_UNTRUSTED environment variable, which libvips reads while initializing.

Applications also running ruby-vips >= 2.2.1 or later can instead call Vips.block_untrusted(true) from an initializer.

Releases

The fixed releases are available at the normal locations.

Versions affected

• activestorage < 7.2.3.2
• activestorage >= 8.0, < 8.0.5.1
• activestorage >= 8.1, < 8.1.3.1

Disclosure

Technical details of the attack chain are intentionally omitted from this advisory. They would add nothing to an administrator's decision to upgrade, while making it substantially easier to attack applications that have not yet done so.

Details will be disclosed no later than 2026-08-28, via the Rails Security Announcements forum.

Credit

This issue was responsibly reported by 0xacb, s3np41k1r1t0 and castilho from Ethiack, and RyotaK from GMO Flatt Security Inc..

References

• libvips 8.13 release notes, blocking of unfuzzed loaders
• W.A. Arbaugh, W.L. Fithen, and J. McHugh, "Windows of Vulnerability: A Case Study Analysis", IEEE Computer 33(12), December 2000
• https://ethiack.com/info-hub/research/kindarails2shell-rails-rce-cve
• https://blog.flatt.tech/entry/kindarails2shell_rails

Impact

Active Storage's proxy controller does not limit the number of byte ranges in an HTTP Range header. A request with thousands of small ranges causes disproportionate CPU usage compared to a normal request for the same file, possibly resulting in a DoS vulnerability.

Releases

The fixed releases are available at the normal locations.

Credit

This issue was responsibly reported by Hackerone researcher thwin_htet.

Impact

Active Storage's DiskService#delete_prefixed passes blob keys directly to Dir.glob without escaping glob metacharacters. If a blob key contains attacker-controlled input or custom-generated keys with glob metacharacters, it may be possible to delete unintended files from the storage directory.

Releases

The fixed releases are available at the normal locations.

Impact

Active Storage's DiskService#path_for does not validate that the resolved filesystem path remains within the storage root directory. If a blob key containing path traversal sequences (e.g. ../) is used, it could allow reading, writing, or deleting arbitrary files on the server. Blob keys are expected to be trusted strings, but some applications could be passing user input as keys and would be affected.

Releases

The fixed releases are available at the normal locations.

Credit

This issue was responsibly reported by Hackerone researcher ksw9722.

Impact

When serving files through Active Storage's Blobs::ProxyController, the controller loads the entire requested byte range into memory before sending it. A request with a large or unbounded Range header (e.g. bytes=0-) could cause the server to allocate memory proportional to the file size, possibly resulting in a DoS vulnerability through memory exhaustion.

Releases

The fixed releases are available at the normal locations.

Credit

This issue was responsibly reported by Hackerone user pirikara

Impact

Active Storage's DirectUploadsController accepts arbitrary metadata from the client and persists it on the blob. Because internal flags like identified and analyzed are stored in the same metadata hash, a malicious direct-upload client could set these flags.

Releases

The fixed releases are available at the normal locations.

Credit

This was responsible reported by Hackerone researcher pwnie

Impact

In its default configuration, a Rails application that displays image variants may allow an unauthenticated attacker to read arbitrary files from the server, including the process environment. That environment typically holds secret_key_base and often credentials for external systems, which may in turn allow escalation to remote code execution or lateral movement to those systems.

Details

libvips reads and writes file formats through "loaders" and "savers" (or more generally "operations"), many of which are backed by third-party libraries. It marks some of these operations as "unfuzzed", meaning they are unsafe for untrusted content, and several handle formats unrelated to web images. Active Storage did not disable the unfuzzed operations, so an attacker who can upload a crafted file and cause a variant to be generated from it may be able to invoke one.

We are aware of a mechanism by which an attacker, by uploading a crafted file, is able to cause disclosure of the contents of arbitrary files accessible on the filesystem of the targeted application. One specific attack chain has been reported to us (see "Disclosure" below), but we do not assume it is the only one that exists.

Affected applications

An application is affected if it meets all of these requirements:

• Uses libvips for Active Storage image processing. This is config.active_storage.variant_processor = :vips, which load_defaults 7.0 set and no later default has changed.
• Allows image uploads from untrusted users.

Generating variants is not a separate requirement.

Mitigation

• Upgrade to a fixed version of activestorage.
• The minimum version of libvips must be upgraded to >= 8.13.
• Change secret_key_base and change any secrets accessible in the application environment (see "Expire and change secrets" below)

Earlier versions of libvips (< 8.13) cannot disable unfuzzed operations at all, and Active Storage will raise an exception during boot in such an unsecurable environment.

Expire and change secrets

Upgrading closes the vulnerability but does not undo an exfiltrated secret if that already occurred. An affected application should treat every secret readable by the application process as potentially exposed and change it, including:

• secret_key_base
• The master key, whether stored in config/master.key or supplied as RAILS_MASTER_KEY, along with everything in config/credentials.yml.enc that it decrypts
• Credentials for the Active Storage service, such as S3, GCS, or Azure keys
• Database credentials
• Tokens and keys for any third-party service the application calls

Changing secret_key_base expires active sessions and requires users to log in again. Encrypted cookies, signed cookies, signed global IDs, and Active Storage URLs are also affected.

Rotation should only be used as an intermediate step if necessary. Do not retain an exposed secret as a fallback.

Workarounds

If libvips < 8.13 is being used, there are no workarounds available other than removing the dependency on libvips from the application. Some applications may have ruby-vips declared as a dependency only for image analysis, and those applications may be able to simply remove ruby-vips from the Gemfile to remove libvips from the application. Applications that do not use Active Storage can remove ruby-vips from the Gemfile to avoid the boot-time checks.

If libvips >= 8.13 is present on the system, applications can disable the unfuzzed operations without upgrading Rails by setting the VIPS_BLOCK_UNTRUSTED environment variable, which libvips reads while initializing.

Applications also running ruby-vips >= 2.2.1 or later can instead call Vips.block_untrusted(true) from an initializer.

Releases

The fixed releases are available at the normal locations.

Versions affected

• activestorage < 7.2.3.2
• activestorage >= 8.0, < 8.0.5.1
• activestorage >= 8.1, < 8.1.3.1

Disclosure

Technical details of the attack chain are intentionally omitted from this advisory. They would add nothing to an administrator's decision to upgrade, while making it substantially easier to attack applications that have not yet done so.

Details will be disclosed no later than 2026-08-28, via the Rails Security Announcements forum.

Credit

This issue was responsibly reported by 0xacb, s3np41k1r1t0 and castilho from Ethiack, and RyotaK from GMO Flatt Security Inc..

References

• libvips 8.13 release notes, blocking of unfuzzed loaders
• W.A. Arbaugh, W.L. Fithen, and J. McHugh, "Windows of Vulnerability: A Case Study Analysis", IEEE Computer 33(12), December 2000
• https://ethiack.com/info-hub/research/kindarails2shell-rails-rce-cve
• https://blog.flatt.tech/entry/kindarails2shell_rails

Impact

Active Storage's proxy controller does not limit the number of byte ranges in an HTTP Range header. A request with thousands of small ranges causes disproportionate CPU usage compared to a normal request for the same file, possibly resulting in a DoS vulnerability.

Releases

The fixed releases are available at the normal locations.

Credit

This issue was responsibly reported by Hackerone researcher thwin_htet.

Impact

Active Storage's DiskService#delete_prefixed passes blob keys directly to Dir.glob without escaping glob metacharacters. If a blob key contains attacker-controlled input or custom-generated keys with glob metacharacters, it may be possible to delete unintended files from the storage directory.

Releases

The fixed releases are available at the normal locations.

Impact

Active Storage's DiskService#path_for does not validate that the resolved filesystem path remains within the storage root directory. If a blob key containing path traversal sequences (e.g. ../) is used, it could allow reading, writing, or deleting arbitrary files on the server. Blob keys are expected to be trusted strings, but some applications could be passing user input as keys and would be affected.

Releases

The fixed releases are available at the normal locations.

Credit

This issue was responsibly reported by Hackerone researcher ksw9722.

Impact

When serving files through Active Storage's Blobs::ProxyController, the controller loads the entire requested byte range into memory before sending it. A request with a large or unbounded Range header (e.g. bytes=0-) could cause the server to allocate memory proportional to the file size, possibly resulting in a DoS vulnerability through memory exhaustion.

Releases

The fixed releases are available at the normal locations.

Credit

This issue was responsibly reported by Hackerone user pirikara

Impact

Active Storage's DirectUploadsController accepts arbitrary metadata from the client and persists it on the blob. Because internal flags like identified and analyzed are stored in the same metadata hash, a malicious direct-upload client could set these flags.

Releases

The fixed releases are available at the normal locations.

Credit

This was responsible reported by Hackerone researcher pwnie

Impact

In its default configuration, a Rails application that displays image variants may allow an unauthenticated attacker to read arbitrary files from the server, including the process environment. That environment typically holds secret_key_base and often credentials for external systems, which may in turn allow escalation to remote code execution or lateral movement to those systems.

Details

libvips reads and writes file formats through "loaders" and "savers" (or more generally "operations"), many of which are backed by third-party libraries. It marks some of these operations as "unfuzzed", meaning they are unsafe for untrusted content, and several handle formats unrelated to web images. Active Storage did not disable the unfuzzed operations, so an attacker who can upload a crafted file and cause a variant to be generated from it may be able to invoke one.

We are aware of a mechanism by which an attacker, by uploading a crafted file, is able to cause disclosure of the contents of arbitrary files accessible on the filesystem of the targeted application. One specific attack chain has been reported to us (see "Disclosure" below), but we do not assume it is the only one that exists.

Affected applications

An application is affected if it meets all of these requirements:

• Uses libvips for Active Storage image processing. This is config.active_storage.variant_processor = :vips, which load_defaults 7.0 set and no later default has changed.
• Allows image uploads from untrusted users.

Generating variants is not a separate requirement.

Mitigation

• Upgrade to a fixed version of activestorage.
• The minimum version of libvips must be upgraded to >= 8.13.
• Change secret_key_base and change any secrets accessible in the application environment (see "Expire and change secrets" below)

Earlier versions of libvips (< 8.13) cannot disable unfuzzed operations at all, and Active Storage will raise an exception during boot in such an unsecurable environment.

Expire and change secrets

Upgrading closes the vulnerability but does not undo an exfiltrated secret if that already occurred. An affected application should treat every secret readable by the application process as potentially exposed and change it, including:

• secret_key_base
• The master key, whether stored in config/master.key or supplied as RAILS_MASTER_KEY, along with everything in config/credentials.yml.enc that it decrypts
• Credentials for the Active Storage service, such as S3, GCS, or Azure keys
• Database credentials
• Tokens and keys for any third-party service the application calls

Changing secret_key_base expires active sessions and requires users to log in again. Encrypted cookies, signed cookies, signed global IDs, and Active Storage URLs are also affected.

Rotation should only be used as an intermediate step if necessary. Do not retain an exposed secret as a fallback.

Workarounds

If libvips < 8.13 is being used, there are no workarounds available other than removing the dependency on libvips from the application. Some applications may have ruby-vips declared as a dependency only for image analysis, and those applications may be able to simply remove ruby-vips from the Gemfile to remove libvips from the application. Applications that do not use Active Storage can remove ruby-vips from the Gemfile to avoid the boot-time checks.

If libvips >= 8.13 is present on the system, applications can disable the unfuzzed operations without upgrading Rails by setting the VIPS_BLOCK_UNTRUSTED environment variable, which libvips reads while initializing.

Applications also running ruby-vips >= 2.2.1 or later can instead call Vips.block_untrusted(true) from an initializer.

Releases

The fixed releases are available at the normal locations.

Versions affected

• activestorage < 7.2.3.2
• activestorage >= 8.0, < 8.0.5.1
• activestorage >= 8.1, < 8.1.3.1

Disclosure

Technical details of the attack chain are intentionally omitted from this advisory. They would add nothing to an administrator's decision to upgrade, while making it substantially easier to attack applications that have not yet done so.

Details will be disclosed no later than 2026-08-28, via the Rails Security Announcements forum.

Credit

This issue was responsibly reported by 0xacb, s3np41k1r1t0 and castilho from Ethiack, and RyotaK from GMO Flatt Security Inc..

References

• libvips 8.13 release notes, blocking of unfuzzed loaders
• W.A. Arbaugh, W.L. Fithen, and J. McHugh, "Windows of Vulnerability: A Case Study Analysis", IEEE Computer 33(12), December 2000
• https://ethiack.com/info-hub/research/kindarails2shell-rails-rce-cve
• https://blog.flatt.tech/entry/kindarails2shell_rails

Impact

Active Storage's proxy controller does not limit the number of byte ranges in an HTTP Range header. A request with thousands of small ranges causes disproportionate CPU usage compared to a normal request for the same file, possibly resulting in a DoS vulnerability.

Releases

The fixed releases are available at the normal locations.

Credit

This issue was responsibly reported by Hackerone researcher thwin_htet.

Impact

Active Storage's DiskService#delete_prefixed passes blob keys directly to Dir.glob without escaping glob metacharacters. If a blob key contains attacker-controlled input or custom-generated keys with glob metacharacters, it may be possible to delete unintended files from the storage directory.

Releases

The fixed releases are available at the normal locations.

Impact

Active Storage's DiskService#path_for does not validate that the resolved filesystem path remains within the storage root directory. If a blob key containing path traversal sequences (e.g. ../) is used, it could allow reading, writing, or deleting arbitrary files on the server. Blob keys are expected to be trusted strings, but some applications could be passing user input as keys and would be affected.

Releases

The fixed releases are available at the normal locations.

Credit

This issue was responsibly reported by Hackerone researcher ksw9722.

Impact

When serving files through Active Storage's Blobs::ProxyController, the controller loads the entire requested byte range into memory before sending it. A request with a large or unbounded Range header (e.g. bytes=0-) could cause the server to allocate memory proportional to the file size, possibly resulting in a DoS vulnerability through memory exhaustion.

Releases

The fixed releases are available at the normal locations.

Credit

This issue was responsibly reported by Hackerone user pirikara