google.golang.org/grpc

Summary

A vulnerability in the xDS RBAC HTTP filter implementation in grpc-go allows remote attackers to bypass authorization policies (specifically DENY rules) by using mixed-case or canonical-case header matchers (e.g., X-Role instead of x-role). Additionally, the safety guards introduced by gRFC A41 to block grpc- prefixed headers can be evaded via variations in casing (e.g., Grpc-Status).

Impact

When an operator defines an RBAC policy referencing headers containing uppercase letters (e.g. X-Role), grpc-go fails to match incoming metadata keys because they are unconditionally lowercased. Because of this case-sensitivity mismatch, a policy designed to block requests containing specific header values fails open: the rule is evaluated as a non-match, and traffic that should have been rejected is served.

Furthermore, gRFC A41 requires rejecting configuration schemas specifying header matchers starting with grpc-. Because this check is executed case-sensitively in grpc-go, attackers can bypass the validation by specifying titles like Grpc-Status.

Patches

The problem is fixed in master and in the 1.83.1 release.

Impact

An unauthenticated remote attacker can initiate a gRPC stream and purposefully fragment their payload into millions of tiny (e.g., 1-byte) HTTP/2 DATA frames. Even if the total payload volume falls within the configured connection and stream flow-control windows, each independent fragment incurs memory overhead due to internal tracking structures and queue allocation.

Repeated fragmentation massively inflates the heap space consumed by the stream. An attacker multiplexing multiple concurrent streams can exhaust the memory bounds of the runtime, forcing a runtime panic or OutOfMemory condition and leading to a remote Denial of Service (DoS).

Patches

The change to fix this issue is merged in master and a patch release, 1.83.1, has been published that contains this fix.

Workarounds

This vulnerability is mitigated by implementing receive buffer compaction. Consecutive small data buffers are automatically coalesced into larger buffers from a shared pool once the overhead is perceived to be excessive relative to actual payload data, drastically minimizing per-frame memory overheads.

This behavior is enabled by default. A temporary escape hatch is provided via the environment variable GRPC_GO_EXPERIMENTAL_ENABLE_RECEIVE_BUFFER_COMPACTION=false to disable the feature if unforeseen issues arise, but it will be removed in a future release.

A vulnerability exists in gRPC-Go servers configured with xds.NewGRPCServer() where a crafted request missing both :authority and Host headers can cause a server panic, resulting in a Denial of Service (DoS).

Servers built with xds.NewGRPCServer install an xDS routing interceptor on every RPC. This interceptor looks up the request’s :authority header to pick a virtual host. The HTTP/2 server transport previously accepted requests that had neither :authority nor Host. When this happened, the xDS routing interceptor attempted to access the first element of an empty slice of authorities, leading to an index out of bounds panic. Since the per-RPC goroutine does not recover from panics, the entire server process would terminate.

This panic occurs in the interceptor pipeline, meaning the transport credentials handshake (TLS, mTLS, or ALTS) and HTTP/2 connection establishment must complete successfully before the crafted request can reach this logic.

• Insecure/Standard TLS: If the server permits insecure (plaintext) connections or standard credentials (where client certs are not checked), any unauthenticated remote attacker can trigger the crash.
• mTLS / ALTS: If strict transport-level authentication is enforced at the network edge or transport layer (e.g., requiring a valid client certificate), the attacker must possess valid transport credentials to initiate the stream and trigger the panic.

Impact

An attacker can cause a complete outage of the gRPC server by sending a request missing both :authority and Host headers, provided they can successfully establish a transport connection.

Patches

The issue has been addressed in master (and backported to 1.83.2 and 1.82.2). The fix updates the HTTP/2 transport layer to reject requests missing both :authority and Host headers early, maintaining consistency with and other gRPC language implementations.

A vulnerability exists in gRPC-Go servers configured with xds.NewGRPCServer() where a crafted request missing both :authority and Host headers can cause a server panic, resulting in a Denial of Service (DoS).

Servers built with xds.NewGRPCServer install an xDS routing interceptor on every RPC. This interceptor looks up the request’s :authority header to pick a virtual host. The HTTP/2 server transport previously accepted requests that had neither :authority nor Host. When this happened, the xDS routing interceptor attempted to access the first element of an empty slice of authorities, leading to an index out of bounds panic. Since the per-RPC goroutine does not recover from panics, the entire server process would terminate.

This panic occurs in the interceptor pipeline, meaning the transport credentials handshake (TLS, mTLS, or ALTS) and HTTP/2 connection establishment must complete successfully before the crafted request can reach this logic.

• Insecure/Standard TLS: If the server permits insecure (plaintext) connections or standard credentials (where client certs are not checked), any unauthenticated remote attacker can trigger the crash.
• mTLS / ALTS: If strict transport-level authentication is enforced at the network edge or transport layer (e.g., requiring a valid client certificate), the attacker must possess valid transport credentials to initiate the stream and trigger the panic.

Impact

An attacker can cause a complete outage of the gRPC server by sending a request missing both :authority and Host headers, provided they can successfully establish a transport connection.

Patches

The issue has been addressed in master (and backported to 1.83.2 and 1.82.2). The fix updates the HTTP/2 transport layer to reject requests missing both :authority and Host headers early, maintaining consistency with and other gRPC language implementations.

A vulnerability exists in gRPC-Go servers configured with xds.NewGRPCServer() where a crafted request missing both :authority and Host headers can cause a server panic, resulting in a Denial of Service (DoS).

Servers built with xds.NewGRPCServer install an xDS routing interceptor on every RPC. This interceptor looks up the request’s :authority header to pick a virtual host. The HTTP/2 server transport previously accepted requests that had neither :authority nor Host. When this happened, the xDS routing interceptor attempted to access the first element of an empty slice of authorities, leading to an index out of bounds panic. Since the per-RPC goroutine does not recover from panics, the entire server process would terminate.

This panic occurs in the interceptor pipeline, meaning the transport credentials handshake (TLS, mTLS, or ALTS) and HTTP/2 connection establishment must complete successfully before the crafted request can reach this logic.

• Insecure/Standard TLS: If the server permits insecure (plaintext) connections or standard credentials (where client certs are not checked), any unauthenticated remote attacker can trigger the crash.
• mTLS / ALTS: If strict transport-level authentication is enforced at the network edge or transport layer (e.g., requiring a valid client certificate), the attacker must possess valid transport credentials to initiate the stream and trigger the panic.

Impact

An attacker can cause a complete outage of the gRPC server by sending a request missing both :authority and Host headers, provided they can successfully establish a transport connection.

Patches

The issue has been addressed in master (and backported to 1.83.2 and 1.82.2). The fix updates the HTTP/2 transport layer to reject requests missing both :authority and Host headers early, maintaining consistency with and other gRPC language implementations.

Summary

A vulnerability in the xDS RBAC HTTP filter implementation in grpc-go allows remote attackers to bypass authorization policies (specifically DENY rules) by using mixed-case or canonical-case header matchers (e.g., X-Role instead of x-role). Additionally, the safety guards introduced by gRFC A41 to block grpc- prefixed headers can be evaded via variations in casing (e.g., Grpc-Status).

Impact

When an operator defines an RBAC policy referencing headers containing uppercase letters (e.g. X-Role), grpc-go fails to match incoming metadata keys because they are unconditionally lowercased. Because of this case-sensitivity mismatch, a policy designed to block requests containing specific header values fails open: the rule is evaluated as a non-match, and traffic that should have been rejected is served.

Furthermore, gRFC A41 requires rejecting configuration schemas specifying header matchers starting with grpc-. Because this check is executed case-sensitively in grpc-go, attackers can bypass the validation by specifying titles like Grpc-Status.

Patches

The problem is fixed in master and in the 1.83.1 release.

Impact

An unauthenticated remote attacker can initiate a gRPC stream and purposefully fragment their payload into millions of tiny (e.g., 1-byte) HTTP/2 DATA frames. Even if the total payload volume falls within the configured connection and stream flow-control windows, each independent fragment incurs memory overhead due to internal tracking structures and queue allocation.

Repeated fragmentation massively inflates the heap space consumed by the stream. An attacker multiplexing multiple concurrent streams can exhaust the memory bounds of the runtime, forcing a runtime panic or OutOfMemory condition and leading to a remote Denial of Service (DoS).

Patches

The change to fix this issue is merged in master and a patch release, 1.83.1, has been published that contains this fix.

Workarounds

This vulnerability is mitigated by implementing receive buffer compaction. Consecutive small data buffers are automatically coalesced into larger buffers from a shared pool once the overhead is perceived to be excessive relative to actual payload data, drastically minimizing per-frame memory overheads.

This behavior is enabled by default. A temporary escape hatch is provided via the environment variable GRPC_GO_EXPERIMENTAL_ENABLE_RECEIVE_BUFFER_COMPACTION=false to disable the feature if unforeseen issues arise, but it will be removed in a future release.

A vulnerability exists in gRPC-Go servers configured with xds.NewGRPCServer() where a crafted request missing both :authority and Host headers can cause a server panic, resulting in a Denial of Service (DoS).

Servers built with xds.NewGRPCServer install an xDS routing interceptor on every RPC. This interceptor looks up the request’s :authority header to pick a virtual host. The HTTP/2 server transport previously accepted requests that had neither :authority nor Host. When this happened, the xDS routing interceptor attempted to access the first element of an empty slice of authorities, leading to an index out of bounds panic. Since the per-RPC goroutine does not recover from panics, the entire server process would terminate.

This panic occurs in the interceptor pipeline, meaning the transport credentials handshake (TLS, mTLS, or ALTS) and HTTP/2 connection establishment must complete successfully before the crafted request can reach this logic.

• Insecure/Standard TLS: If the server permits insecure (plaintext) connections or standard credentials (where client certs are not checked), any unauthenticated remote attacker can trigger the crash.
• mTLS / ALTS: If strict transport-level authentication is enforced at the network edge or transport layer (e.g., requiring a valid client certificate), the attacker must possess valid transport credentials to initiate the stream and trigger the panic.

Impact

An attacker can cause a complete outage of the gRPC server by sending a request missing both :authority and Host headers, provided they can successfully establish a transport connection.

Patches

The issue has been addressed in master (and backported to 1.83.2 and 1.82.2). The fix updates the HTTP/2 transport layer to reject requests missing both :authority and Host headers early, maintaining consistency with and other gRPC language implementations.

Summary

A vulnerability in the xDS RBAC HTTP filter implementation in grpc-go allows remote attackers to bypass authorization policies (specifically DENY rules) by using mixed-case or canonical-case header matchers (e.g., X-Role instead of x-role). Additionally, the safety guards introduced by gRFC A41 to block grpc- prefixed headers can be evaded via variations in casing (e.g., Grpc-Status).

Impact

When an operator defines an RBAC policy referencing headers containing uppercase letters (e.g. X-Role), grpc-go fails to match incoming metadata keys because they are unconditionally lowercased. Because of this case-sensitivity mismatch, a policy designed to block requests containing specific header values fails open: the rule is evaluated as a non-match, and traffic that should have been rejected is served.

Furthermore, gRFC A41 requires rejecting configuration schemas specifying header matchers starting with grpc-. Because this check is executed case-sensitively in grpc-go, attackers can bypass the validation by specifying titles like Grpc-Status.

Patches

The problem is fixed in master and in the 1.83.1 release.

Impact

An unauthenticated remote attacker can initiate a gRPC stream and purposefully fragment their payload into millions of tiny (e.g., 1-byte) HTTP/2 DATA frames. Even if the total payload volume falls within the configured connection and stream flow-control windows, each independent fragment incurs memory overhead due to internal tracking structures and queue allocation.

Repeated fragmentation massively inflates the heap space consumed by the stream. An attacker multiplexing multiple concurrent streams can exhaust the memory bounds of the runtime, forcing a runtime panic or OutOfMemory condition and leading to a remote Denial of Service (DoS).

Patches

The change to fix this issue is merged in master and a patch release, 1.83.1, has been published that contains this fix.

Workarounds

This vulnerability is mitigated by implementing receive buffer compaction. Consecutive small data buffers are automatically coalesced into larger buffers from a shared pool once the overhead is perceived to be excessive relative to actual payload data, drastically minimizing per-frame memory overheads.

This behavior is enabled by default. A temporary escape hatch is provided via the environment variable GRPC_GO_EXPERIMENTAL_ENABLE_RECEIVE_BUFFER_COMPACTION=false to disable the feature if unforeseen issues arise, but it will be removed in a future release.

A vulnerability exists in gRPC-Go servers configured with xds.NewGRPCServer() where a crafted request missing both :authority and Host headers can cause a server panic, resulting in a Denial of Service (DoS).

Servers built with xds.NewGRPCServer install an xDS routing interceptor on every RPC. This interceptor looks up the request’s :authority header to pick a virtual host. The HTTP/2 server transport previously accepted requests that had neither :authority nor Host. When this happened, the xDS routing interceptor attempted to access the first element of an empty slice of authorities, leading to an index out of bounds panic. Since the per-RPC goroutine does not recover from panics, the entire server process would terminate.

This panic occurs in the interceptor pipeline, meaning the transport credentials handshake (TLS, mTLS, or ALTS) and HTTP/2 connection establishment must complete successfully before the crafted request can reach this logic.

• Insecure/Standard TLS: If the server permits insecure (plaintext) connections or standard credentials (where client certs are not checked), any unauthenticated remote attacker can trigger the crash.
• mTLS / ALTS: If strict transport-level authentication is enforced at the network edge or transport layer (e.g., requiring a valid client certificate), the attacker must possess valid transport credentials to initiate the stream and trigger the panic.

Impact

An attacker can cause a complete outage of the gRPC server by sending a request missing both :authority and Host headers, provided they can successfully establish a transport connection.

Patches

The issue has been addressed in master (and backported to 1.83.2 and 1.82.2). The fix updates the HTTP/2 transport layer to reject requests missing both :authority and Host headers early, maintaining consistency with and other gRPC language implementations.

A vulnerability exists in gRPC-Go servers configured with xds.NewGRPCServer() where a crafted request missing both :authority and Host headers can cause a server panic, resulting in a Denial of Service (DoS).

Servers built with xds.NewGRPCServer install an xDS routing interceptor on every RPC. This interceptor looks up the request’s :authority header to pick a virtual host. The HTTP/2 server transport previously accepted requests that had neither :authority nor Host. When this happened, the xDS routing interceptor attempted to access the first element of an empty slice of authorities, leading to an index out of bounds panic. Since the per-RPC goroutine does not recover from panics, the entire server process would terminate.

This panic occurs in the interceptor pipeline, meaning the transport credentials handshake (TLS, mTLS, or ALTS) and HTTP/2 connection establishment must complete successfully before the crafted request can reach this logic.

• Insecure/Standard TLS: If the server permits insecure (plaintext) connections or standard credentials (where client certs are not checked), any unauthenticated remote attacker can trigger the crash.
• mTLS / ALTS: If strict transport-level authentication is enforced at the network edge or transport layer (e.g., requiring a valid client certificate), the attacker must possess valid transport credentials to initiate the stream and trigger the panic.

Impact

An attacker can cause a complete outage of the gRPC server by sending a request missing both :authority and Host headers, provided they can successfully establish a transport connection.

Patches

The issue has been addressed in master (and backported to 1.83.2 and 1.82.2). The fix updates the HTTP/2 transport layer to reject requests missing both :authority and Host headers early, maintaining consistency with and other gRPC language implementations.

Summary

A vulnerability in the xDS RBAC HTTP filter implementation in grpc-go allows remote attackers to bypass authorization policies (specifically DENY rules) by using mixed-case or canonical-case header matchers (e.g., X-Role instead of x-role). Additionally, the safety guards introduced by gRFC A41 to block grpc- prefixed headers can be evaded via variations in casing (e.g., Grpc-Status).

Impact

When an operator defines an RBAC policy referencing headers containing uppercase letters (e.g. X-Role), grpc-go fails to match incoming metadata keys because they are unconditionally lowercased. Because of this case-sensitivity mismatch, a policy designed to block requests containing specific header values fails open: the rule is evaluated as a non-match, and traffic that should have been rejected is served.

Furthermore, gRFC A41 requires rejecting configuration schemas specifying header matchers starting with grpc-. Because this check is executed case-sensitively in grpc-go, attackers can bypass the validation by specifying titles like Grpc-Status.

Patches

The problem is fixed in master and in the 1.83.1 release.

Impact

An unauthenticated remote attacker can initiate a gRPC stream and purposefully fragment their payload into millions of tiny (e.g., 1-byte) HTTP/2 DATA frames. Even if the total payload volume falls within the configured connection and stream flow-control windows, each independent fragment incurs memory overhead due to internal tracking structures and queue allocation.

Repeated fragmentation massively inflates the heap space consumed by the stream. An attacker multiplexing multiple concurrent streams can exhaust the memory bounds of the runtime, forcing a runtime panic or OutOfMemory condition and leading to a remote Denial of Service (DoS).

Patches

The change to fix this issue is merged in master and a patch release, 1.83.1, has been published that contains this fix.

Workarounds

This vulnerability is mitigated by implementing receive buffer compaction. Consecutive small data buffers are automatically coalesced into larger buffers from a shared pool once the overhead is perceived to be excessive relative to actual payload data, drastically minimizing per-frame memory overheads.

This behavior is enabled by default. A temporary escape hatch is provided via the environment variable GRPC_GO_EXPERIMENTAL_ENABLE_RECEIVE_BUFFER_COMPACTION=false to disable the feature if unforeseen issues arise, but it will be removed in a future release.

Vulnerabilities in the xDS RBAC authorization engine and the HTTP/2 transport server implementation in google.golang.org/grpc

Summary

A vulnerability in the xDS RBAC HTTP filter implementation in grpc-go allows remote attackers to bypass authorization policies (specifically DENY rules) by using mixed-case or canonical-case header matchers (e.g., X-Role instead of x-role). Additionally, the safety guards introduced by gRFC A41 to block grpc- prefixed headers can be evaded via variations in casing (e.g., Grpc-Status).

Impact

When an operator defines an RBAC policy referencing headers containing uppercase letters (e.g. X-Role), grpc-go fails to match incoming metadata keys because they are unconditionally lowercased. Because of this case-sensitivity mismatch, a policy designed to block requests containing specific header values fails open: the rule is evaluated as a non-match, and traffic that should have been rejected is served.

Furthermore, gRFC A41 requires rejecting configuration schemas specifying header matchers starting with grpc-. Because this check is executed case-sensitively in grpc-go, attackers can bypass the validation by specifying titles like Grpc-Status.

Patches

The problem is fixed in master and in the 1.83.1 release.

Impact

An unauthenticated remote attacker can initiate a gRPC stream and purposefully fragment their payload into millions of tiny (e.g., 1-byte) HTTP/2 DATA frames. Even if the total payload volume falls within the configured connection and stream flow-control windows, each independent fragment incurs memory overhead due to internal tracking structures and queue allocation.

Repeated fragmentation massively inflates the heap space consumed by the stream. An attacker multiplexing multiple concurrent streams can exhaust the memory bounds of the runtime, forcing a runtime panic or OutOfMemory condition and leading to a remote Denial of Service (DoS).

Patches

The change to fix this issue is merged in master and a patch release, 1.83.1, has been published that contains this fix.

Workarounds

This vulnerability is mitigated by implementing receive buffer compaction. Consecutive small data buffers are automatically coalesced into larger buffers from a shared pool once the overhead is perceived to be excessive relative to actual payload data, drastically minimizing per-frame memory overheads.

This behavior is enabled by default. A temporary escape hatch is provided via the environment variable GRPC_GO_EXPERIMENTAL_ENABLE_RECEIVE_BUFFER_COMPACTION=false to disable the feature if unforeseen issues arise, but it will be removed in a future release.

A vulnerability exists in gRPC-Go servers configured with xds.NewGRPCServer() where a crafted request missing both :authority and Host headers can cause a server panic, resulting in a Denial of Service (DoS).

Servers built with xds.NewGRPCServer install an xDS routing interceptor on every RPC. This interceptor looks up the request’s :authority header to pick a virtual host. The HTTP/2 server transport previously accepted requests that had neither :authority nor Host. When this happened, the xDS routing interceptor attempted to access the first element of an empty slice of authorities, leading to an index out of bounds panic. Since the per-RPC goroutine does not recover from panics, the entire server process would terminate.

This panic occurs in the interceptor pipeline, meaning the transport credentials handshake (TLS, mTLS, or ALTS) and HTTP/2 connection establishment must complete successfully before the crafted request can reach this logic.

• Insecure/Standard TLS: If the server permits insecure (plaintext) connections or standard credentials (where client certs are not checked), any unauthenticated remote attacker can trigger the crash.
• mTLS / ALTS: If strict transport-level authentication is enforced at the network edge or transport layer (e.g., requiring a valid client certificate), the attacker must possess valid transport credentials to initiate the stream and trigger the panic.

Impact

An attacker can cause a complete outage of the gRPC server by sending a request missing both :authority and Host headers, provided they can successfully establish a transport connection.

Patches

The issue has been addressed in master (and backported to 1.83.2 and 1.82.2). The fix updates the HTTP/2 transport layer to reject requests missing both :authority and Host headers early, maintaining consistency with and other gRPC language implementations.

Summary

A vulnerability in the xDS RBAC HTTP filter implementation in grpc-go allows remote attackers to bypass authorization policies (specifically DENY rules) by using mixed-case or canonical-case header matchers (e.g., X-Role instead of x-role). Additionally, the safety guards introduced by gRFC A41 to block grpc- prefixed headers can be evaded via variations in casing (e.g., Grpc-Status).

Impact

When an operator defines an RBAC policy referencing headers containing uppercase letters (e.g. X-Role), grpc-go fails to match incoming metadata keys because they are unconditionally lowercased. Because of this case-sensitivity mismatch, a policy designed to block requests containing specific header values fails open: the rule is evaluated as a non-match, and traffic that should have been rejected is served.

Furthermore, gRFC A41 requires rejecting configuration schemas specifying header matchers starting with grpc-. Because this check is executed case-sensitively in grpc-go, attackers can bypass the validation by specifying titles like Grpc-Status.

Patches

The problem is fixed in master and in the 1.83.1 release.

Impact

An unauthenticated remote attacker can initiate a gRPC stream and purposefully fragment their payload into millions of tiny (e.g., 1-byte) HTTP/2 DATA frames. Even if the total payload volume falls within the configured connection and stream flow-control windows, each independent fragment incurs memory overhead due to internal tracking structures and queue allocation.

Repeated fragmentation massively inflates the heap space consumed by the stream. An attacker multiplexing multiple concurrent streams can exhaust the memory bounds of the runtime, forcing a runtime panic or OutOfMemory condition and leading to a remote Denial of Service (DoS).

Patches

The change to fix this issue is merged in master and a patch release, 1.83.1, has been published that contains this fix.

Workarounds

This vulnerability is mitigated by implementing receive buffer compaction. Consecutive small data buffers are automatically coalesced into larger buffers from a shared pool once the overhead is perceived to be excessive relative to actual payload data, drastically minimizing per-frame memory overheads.

This behavior is enabled by default. A temporary escape hatch is provided via the environment variable GRPC_GO_EXPERIMENTAL_ENABLE_RECEIVE_BUFFER_COMPACTION=false to disable the feature if unforeseen issues arise, but it will be removed in a future release.

Vulnerabilities in the xDS RBAC authorization engine and the HTTP/2 transport server implementation in google.golang.org/grpc

A vulnerability exists in gRPC-Go servers configured with xds.NewGRPCServer() where a crafted request missing both :authority and Host headers can cause a server panic, resulting in a Denial of Service (DoS).

Servers built with xds.NewGRPCServer install an xDS routing interceptor on every RPC. This interceptor looks up the request’s :authority header to pick a virtual host. The HTTP/2 server transport previously accepted requests that had neither :authority nor Host. When this happened, the xDS routing interceptor attempted to access the first element of an empty slice of authorities, leading to an index out of bounds panic. Since the per-RPC goroutine does not recover from panics, the entire server process would terminate.

This panic occurs in the interceptor pipeline, meaning the transport credentials handshake (TLS, mTLS, or ALTS) and HTTP/2 connection establishment must complete successfully before the crafted request can reach this logic.

• Insecure/Standard TLS: If the server permits insecure (plaintext) connections or standard credentials (where client certs are not checked), any unauthenticated remote attacker can trigger the crash.
• mTLS / ALTS: If strict transport-level authentication is enforced at the network edge or transport layer (e.g., requiring a valid client certificate), the attacker must possess valid transport credentials to initiate the stream and trigger the panic.

Impact

An attacker can cause a complete outage of the gRPC server by sending a request missing both :authority and Host headers, provided they can successfully establish a transport connection.

Patches

The issue has been addressed in master (and backported to 1.83.2 and 1.82.2). The fix updates the HTTP/2 transport layer to reject requests missing both :authority and Host headers early, maintaining consistency with and other gRPC language implementations.

Summary

A vulnerability in the xDS RBAC HTTP filter implementation in grpc-go allows remote attackers to bypass authorization policies (specifically DENY rules) by using mixed-case or canonical-case header matchers (e.g., X-Role instead of x-role). Additionally, the safety guards introduced by gRFC A41 to block grpc- prefixed headers can be evaded via variations in casing (e.g., Grpc-Status).

Impact

When an operator defines an RBAC policy referencing headers containing uppercase letters (e.g. X-Role), grpc-go fails to match incoming metadata keys because they are unconditionally lowercased. Because of this case-sensitivity mismatch, a policy designed to block requests containing specific header values fails open: the rule is evaluated as a non-match, and traffic that should have been rejected is served.

Furthermore, gRFC A41 requires rejecting configuration schemas specifying header matchers starting with grpc-. Because this check is executed case-sensitively in grpc-go, attackers can bypass the validation by specifying titles like Grpc-Status.

Patches

The problem is fixed in master and in the 1.83.1 release.

Impact

An unauthenticated remote attacker can initiate a gRPC stream and purposefully fragment their payload into millions of tiny (e.g., 1-byte) HTTP/2 DATA frames. Even if the total payload volume falls within the configured connection and stream flow-control windows, each independent fragment incurs memory overhead due to internal tracking structures and queue allocation.

Repeated fragmentation massively inflates the heap space consumed by the stream. An attacker multiplexing multiple concurrent streams can exhaust the memory bounds of the runtime, forcing a runtime panic or OutOfMemory condition and leading to a remote Denial of Service (DoS).

Patches

The change to fix this issue is merged in master and a patch release, 1.83.1, has been published that contains this fix.

Workarounds

This vulnerability is mitigated by implementing receive buffer compaction. Consecutive small data buffers are automatically coalesced into larger buffers from a shared pool once the overhead is perceived to be excessive relative to actual payload data, drastically minimizing per-frame memory overheads.

This behavior is enabled by default. A temporary escape hatch is provided via the environment variable GRPC_GO_EXPERIMENTAL_ENABLE_RECEIVE_BUFFER_COMPACTION=false to disable the feature if unforeseen issues arise, but it will be removed in a future release.

Vulnerabilities in the xDS RBAC authorization engine and the HTTP/2 transport server implementation in google.golang.org/grpc

A vulnerability exists in gRPC-Go servers configured with xds.NewGRPCServer() where a crafted request missing both :authority and Host headers can cause a server panic, resulting in a Denial of Service (DoS).

Servers built with xds.NewGRPCServer install an xDS routing interceptor on every RPC. This interceptor looks up the request’s :authority header to pick a virtual host. The HTTP/2 server transport previously accepted requests that had neither :authority nor Host. When this happened, the xDS routing interceptor attempted to access the first element of an empty slice of authorities, leading to an index out of bounds panic. Since the per-RPC goroutine does not recover from panics, the entire server process would terminate.

This panic occurs in the interceptor pipeline, meaning the transport credentials handshake (TLS, mTLS, or ALTS) and HTTP/2 connection establishment must complete successfully before the crafted request can reach this logic.

• Insecure/Standard TLS: If the server permits insecure (plaintext) connections or standard credentials (where client certs are not checked), any unauthenticated remote attacker can trigger the crash.
• mTLS / ALTS: If strict transport-level authentication is enforced at the network edge or transport layer (e.g., requiring a valid client certificate), the attacker must possess valid transport credentials to initiate the stream and trigger the panic.

Impact

An attacker can cause a complete outage of the gRPC server by sending a request missing both :authority and Host headers, provided they can successfully establish a transport connection.

Patches

The issue has been addressed in master (and backported to 1.83.2 and 1.82.2). The fix updates the HTTP/2 transport layer to reject requests missing both :authority and Host headers early, maintaining consistency with and other gRPC language implementations.

Summary

A vulnerability in the xDS RBAC HTTP filter implementation in grpc-go allows remote attackers to bypass authorization policies (specifically DENY rules) by using mixed-case or canonical-case header matchers (e.g., X-Role instead of x-role). Additionally, the safety guards introduced by gRFC A41 to block grpc- prefixed headers can be evaded via variations in casing (e.g., Grpc-Status).

Impact

When an operator defines an RBAC policy referencing headers containing uppercase letters (e.g. X-Role), grpc-go fails to match incoming metadata keys because they are unconditionally lowercased. Because of this case-sensitivity mismatch, a policy designed to block requests containing specific header values fails open: the rule is evaluated as a non-match, and traffic that should have been rejected is served.

Furthermore, gRFC A41 requires rejecting configuration schemas specifying header matchers starting with grpc-. Because this check is executed case-sensitively in grpc-go, attackers can bypass the validation by specifying titles like Grpc-Status.

Patches

The problem is fixed in master and in the 1.83.1 release.

Impact

An unauthenticated remote attacker can initiate a gRPC stream and purposefully fragment their payload into millions of tiny (e.g., 1-byte) HTTP/2 DATA frames. Even if the total payload volume falls within the configured connection and stream flow-control windows, each independent fragment incurs memory overhead due to internal tracking structures and queue allocation.

Repeated fragmentation massively inflates the heap space consumed by the stream. An attacker multiplexing multiple concurrent streams can exhaust the memory bounds of the runtime, forcing a runtime panic or OutOfMemory condition and leading to a remote Denial of Service (DoS).

Patches

The change to fix this issue is merged in master and a patch release, 1.83.1, has been published that contains this fix.

Workarounds

This vulnerability is mitigated by implementing receive buffer compaction. Consecutive small data buffers are automatically coalesced into larger buffers from a shared pool once the overhead is perceived to be excessive relative to actual payload data, drastically minimizing per-frame memory overheads.

This behavior is enabled by default. A temporary escape hatch is provided via the environment variable GRPC_GO_EXPERIMENTAL_ENABLE_RECEIVE_BUFFER_COMPACTION=false to disable the feature if unforeseen issues arise, but it will be removed in a future release.

Vulnerabilities in the xDS RBAC authorization engine and the HTTP/2 transport server implementation in google.golang.org/grpc

A vulnerability exists in gRPC-Go servers configured with xds.NewGRPCServer() where a crafted request missing both :authority and Host headers can cause a server panic, resulting in a Denial of Service (DoS).

Servers built with xds.NewGRPCServer install an xDS routing interceptor on every RPC. This interceptor looks up the request’s :authority header to pick a virtual host. The HTTP/2 server transport previously accepted requests that had neither :authority nor Host. When this happened, the xDS routing interceptor attempted to access the first element of an empty slice of authorities, leading to an index out of bounds panic. Since the per-RPC goroutine does not recover from panics, the entire server process would terminate.

This panic occurs in the interceptor pipeline, meaning the transport credentials handshake (TLS, mTLS, or ALTS) and HTTP/2 connection establishment must complete successfully before the crafted request can reach this logic.

• Insecure/Standard TLS: If the server permits insecure (plaintext) connections or standard credentials (where client certs are not checked), any unauthenticated remote attacker can trigger the crash.
• mTLS / ALTS: If strict transport-level authentication is enforced at the network edge or transport layer (e.g., requiring a valid client certificate), the attacker must possess valid transport credentials to initiate the stream and trigger the panic.

Impact

An attacker can cause a complete outage of the gRPC server by sending a request missing both :authority and Host headers, provided they can successfully establish a transport connection.

Patches

The issue has been addressed in master (and backported to 1.83.2 and 1.82.2). The fix updates the HTTP/2 transport layer to reject requests missing both :authority and Host headers early, maintaining consistency with and other gRPC language implementations.

Summary

A vulnerability in the xDS RBAC HTTP filter implementation in grpc-go allows remote attackers to bypass authorization policies (specifically DENY rules) by using mixed-case or canonical-case header matchers (e.g., X-Role instead of x-role). Additionally, the safety guards introduced by gRFC A41 to block grpc- prefixed headers can be evaded via variations in casing (e.g., Grpc-Status).

Impact

When an operator defines an RBAC policy referencing headers containing uppercase letters (e.g. X-Role), grpc-go fails to match incoming metadata keys because they are unconditionally lowercased. Because of this case-sensitivity mismatch, a policy designed to block requests containing specific header values fails open: the rule is evaluated as a non-match, and traffic that should have been rejected is served.

Furthermore, gRFC A41 requires rejecting configuration schemas specifying header matchers starting with grpc-. Because this check is executed case-sensitively in grpc-go, attackers can bypass the validation by specifying titles like Grpc-Status.

Patches

The problem is fixed in master and in the 1.83.1 release.

Impact

An unauthenticated remote attacker can initiate a gRPC stream and purposefully fragment their payload into millions of tiny (e.g., 1-byte) HTTP/2 DATA frames. Even if the total payload volume falls within the configured connection and stream flow-control windows, each independent fragment incurs memory overhead due to internal tracking structures and queue allocation.

Repeated fragmentation massively inflates the heap space consumed by the stream. An attacker multiplexing multiple concurrent streams can exhaust the memory bounds of the runtime, forcing a runtime panic or OutOfMemory condition and leading to a remote Denial of Service (DoS).

Patches

The change to fix this issue is merged in master and a patch release, 1.83.1, has been published that contains this fix.

Workarounds

This vulnerability is mitigated by implementing receive buffer compaction. Consecutive small data buffers are automatically coalesced into larger buffers from a shared pool once the overhead is perceived to be excessive relative to actual payload data, drastically minimizing per-frame memory overheads.

This behavior is enabled by default. A temporary escape hatch is provided via the environment variable GRPC_GO_EXPERIMENTAL_ENABLE_RECEIVE_BUFFER_COMPACTION=false to disable the feature if unforeseen issues arise, but it will be removed in a future release.

Vulnerabilities in the xDS RBAC authorization engine and the HTTP/2 transport server implementation in google.golang.org/grpc

A vulnerability exists in gRPC-Go servers configured with xds.NewGRPCServer() where a crafted request missing both :authority and Host headers can cause a server panic, resulting in a Denial of Service (DoS).

Servers built with xds.NewGRPCServer install an xDS routing interceptor on every RPC. This interceptor looks up the request’s :authority header to pick a virtual host. The HTTP/2 server transport previously accepted requests that had neither :authority nor Host. When this happened, the xDS routing interceptor attempted to access the first element of an empty slice of authorities, leading to an index out of bounds panic. Since the per-RPC goroutine does not recover from panics, the entire server process would terminate.

This panic occurs in the interceptor pipeline, meaning the transport credentials handshake (TLS, mTLS, or ALTS) and HTTP/2 connection establishment must complete successfully before the crafted request can reach this logic.

• Insecure/Standard TLS: If the server permits insecure (plaintext) connections or standard credentials (where client certs are not checked), any unauthenticated remote attacker can trigger the crash.
• mTLS / ALTS: If strict transport-level authentication is enforced at the network edge or transport layer (e.g., requiring a valid client certificate), the attacker must possess valid transport credentials to initiate the stream and trigger the panic.

Impact

An attacker can cause a complete outage of the gRPC server by sending a request missing both :authority and Host headers, provided they can successfully establish a transport connection.

Patches

The issue has been addressed in master (and backported to 1.83.2 and 1.82.2). The fix updates the HTTP/2 transport layer to reject requests missing both :authority and Host headers early, maintaining consistency with and other gRPC language implementations.

Summary

A vulnerability in the xDS RBAC HTTP filter implementation in grpc-go allows remote attackers to bypass authorization policies (specifically DENY rules) by using mixed-case or canonical-case header matchers (e.g., X-Role instead of x-role). Additionally, the safety guards introduced by gRFC A41 to block grpc- prefixed headers can be evaded via variations in casing (e.g., Grpc-Status).

Impact

When an operator defines an RBAC policy referencing headers containing uppercase letters (e.g. X-Role), grpc-go fails to match incoming metadata keys because they are unconditionally lowercased. Because of this case-sensitivity mismatch, a policy designed to block requests containing specific header values fails open: the rule is evaluated as a non-match, and traffic that should have been rejected is served.

Furthermore, gRFC A41 requires rejecting configuration schemas specifying header matchers starting with grpc-. Because this check is executed case-sensitively in grpc-go, attackers can bypass the validation by specifying titles like Grpc-Status.

Patches

The problem is fixed in master and in the 1.83.1 release.

Impact

An unauthenticated remote attacker can initiate a gRPC stream and purposefully fragment their payload into millions of tiny (e.g., 1-byte) HTTP/2 DATA frames. Even if the total payload volume falls within the configured connection and stream flow-control windows, each independent fragment incurs memory overhead due to internal tracking structures and queue allocation.

Repeated fragmentation massively inflates the heap space consumed by the stream. An attacker multiplexing multiple concurrent streams can exhaust the memory bounds of the runtime, forcing a runtime panic or OutOfMemory condition and leading to a remote Denial of Service (DoS).

Patches

The change to fix this issue is merged in master and a patch release, 1.83.1, has been published that contains this fix.

Workarounds

This vulnerability is mitigated by implementing receive buffer compaction. Consecutive small data buffers are automatically coalesced into larger buffers from a shared pool once the overhead is perceived to be excessive relative to actual payload data, drastically minimizing per-frame memory overheads.

This behavior is enabled by default. A temporary escape hatch is provided via the environment variable GRPC_GO_EXPERIMENTAL_ENABLE_RECEIVE_BUFFER_COMPACTION=false to disable the feature if unforeseen issues arise, but it will be removed in a future release.

Vulnerabilities in the xDS RBAC authorization engine and the HTTP/2 transport server implementation in google.golang.org/grpc

A vulnerability exists in gRPC-Go servers configured with xds.NewGRPCServer() where a crafted request missing both :authority and Host headers can cause a server panic, resulting in a Denial of Service (DoS).

Servers built with xds.NewGRPCServer install an xDS routing interceptor on every RPC. This interceptor looks up the request’s :authority header to pick a virtual host. The HTTP/2 server transport previously accepted requests that had neither :authority nor Host. When this happened, the xDS routing interceptor attempted to access the first element of an empty slice of authorities, leading to an index out of bounds panic. Since the per-RPC goroutine does not recover from panics, the entire server process would terminate.

This panic occurs in the interceptor pipeline, meaning the transport credentials handshake (TLS, mTLS, or ALTS) and HTTP/2 connection establishment must complete successfully before the crafted request can reach this logic.

• Insecure/Standard TLS: If the server permits insecure (plaintext) connections or standard credentials (where client certs are not checked), any unauthenticated remote attacker can trigger the crash.
• mTLS / ALTS: If strict transport-level authentication is enforced at the network edge or transport layer (e.g., requiring a valid client certificate), the attacker must possess valid transport credentials to initiate the stream and trigger the panic.

Impact

An attacker can cause a complete outage of the gRPC server by sending a request missing both :authority and Host headers, provided they can successfully establish a transport connection.

Patches

The issue has been addressed in master (and backported to 1.83.2 and 1.82.2). The fix updates the HTTP/2 transport layer to reject requests missing both :authority and Host headers early, maintaining consistency with and other gRPC language implementations.

Summary

A vulnerability in the xDS RBAC HTTP filter implementation in grpc-go allows remote attackers to bypass authorization policies (specifically DENY rules) by using mixed-case or canonical-case header matchers (e.g., X-Role instead of x-role). Additionally, the safety guards introduced by gRFC A41 to block grpc- prefixed headers can be evaded via variations in casing (e.g., Grpc-Status).

Impact

When an operator defines an RBAC policy referencing headers containing uppercase letters (e.g. X-Role), grpc-go fails to match incoming metadata keys because they are unconditionally lowercased. Because of this case-sensitivity mismatch, a policy designed to block requests containing specific header values fails open: the rule is evaluated as a non-match, and traffic that should have been rejected is served.

Furthermore, gRFC A41 requires rejecting configuration schemas specifying header matchers starting with grpc-. Because this check is executed case-sensitively in grpc-go, attackers can bypass the validation by specifying titles like Grpc-Status.

Patches

The problem is fixed in master and in the 1.83.1 release.

Impact

An unauthenticated remote attacker can initiate a gRPC stream and purposefully fragment their payload into millions of tiny (e.g., 1-byte) HTTP/2 DATA frames. Even if the total payload volume falls within the configured connection and stream flow-control windows, each independent fragment incurs memory overhead due to internal tracking structures and queue allocation.

Repeated fragmentation massively inflates the heap space consumed by the stream. An attacker multiplexing multiple concurrent streams can exhaust the memory bounds of the runtime, forcing a runtime panic or OutOfMemory condition and leading to a remote Denial of Service (DoS).

Patches

The change to fix this issue is merged in master and a patch release, 1.83.1, has been published that contains this fix.

Workarounds

This vulnerability is mitigated by implementing receive buffer compaction. Consecutive small data buffers are automatically coalesced into larger buffers from a shared pool once the overhead is perceived to be excessive relative to actual payload data, drastically minimizing per-frame memory overheads.

This behavior is enabled by default. A temporary escape hatch is provided via the environment variable GRPC_GO_EXPERIMENTAL_ENABLE_RECEIVE_BUFFER_COMPACTION=false to disable the feature if unforeseen issues arise, but it will be removed in a future release.

Vulnerabilities in the xDS RBAC authorization engine and the HTTP/2 transport server implementation in google.golang.org/grpc

A vulnerability exists in gRPC-Go servers configured with xds.NewGRPCServer() where a crafted request missing both :authority and Host headers can cause a server panic, resulting in a Denial of Service (DoS).

Servers built with xds.NewGRPCServer install an xDS routing interceptor on every RPC. This interceptor looks up the request’s :authority header to pick a virtual host. The HTTP/2 server transport previously accepted requests that had neither :authority nor Host. When this happened, the xDS routing interceptor attempted to access the first element of an empty slice of authorities, leading to an index out of bounds panic. Since the per-RPC goroutine does not recover from panics, the entire server process would terminate.

This panic occurs in the interceptor pipeline, meaning the transport credentials handshake (TLS, mTLS, or ALTS) and HTTP/2 connection establishment must complete successfully before the crafted request can reach this logic.

• Insecure/Standard TLS: If the server permits insecure (plaintext) connections or standard credentials (where client certs are not checked), any unauthenticated remote attacker can trigger the crash.
• mTLS / ALTS: If strict transport-level authentication is enforced at the network edge or transport layer (e.g., requiring a valid client certificate), the attacker must possess valid transport credentials to initiate the stream and trigger the panic.

Impact

An attacker can cause a complete outage of the gRPC server by sending a request missing both :authority and Host headers, provided they can successfully establish a transport connection.

Patches

The issue has been addressed in master (and backported to 1.83.2 and 1.82.2). The fix updates the HTTP/2 transport layer to reject requests missing both :authority and Host headers early, maintaining consistency with and other gRPC language implementations.

Summary

A vulnerability in the xDS RBAC HTTP filter implementation in grpc-go allows remote attackers to bypass authorization policies (specifically DENY rules) by using mixed-case or canonical-case header matchers (e.g., X-Role instead of x-role). Additionally, the safety guards introduced by gRFC A41 to block grpc- prefixed headers can be evaded via variations in casing (e.g., Grpc-Status).

Impact

When an operator defines an RBAC policy referencing headers containing uppercase letters (e.g. X-Role), grpc-go fails to match incoming metadata keys because they are unconditionally lowercased. Because of this case-sensitivity mismatch, a policy designed to block requests containing specific header values fails open: the rule is evaluated as a non-match, and traffic that should have been rejected is served.

Furthermore, gRFC A41 requires rejecting configuration schemas specifying header matchers starting with grpc-. Because this check is executed case-sensitively in grpc-go, attackers can bypass the validation by specifying titles like Grpc-Status.

Patches

The problem is fixed in master and in the 1.83.1 release.

Impact

An unauthenticated remote attacker can initiate a gRPC stream and purposefully fragment their payload into millions of tiny (e.g., 1-byte) HTTP/2 DATA frames. Even if the total payload volume falls within the configured connection and stream flow-control windows, each independent fragment incurs memory overhead due to internal tracking structures and queue allocation.

Repeated fragmentation massively inflates the heap space consumed by the stream. An attacker multiplexing multiple concurrent streams can exhaust the memory bounds of the runtime, forcing a runtime panic or OutOfMemory condition and leading to a remote Denial of Service (DoS).

Patches

The change to fix this issue is merged in master and a patch release, 1.83.1, has been published that contains this fix.

Workarounds

This vulnerability is mitigated by implementing receive buffer compaction. Consecutive small data buffers are automatically coalesced into larger buffers from a shared pool once the overhead is perceived to be excessive relative to actual payload data, drastically minimizing per-frame memory overheads.

This behavior is enabled by default. A temporary escape hatch is provided via the environment variable GRPC_GO_EXPERIMENTAL_ENABLE_RECEIVE_BUFFER_COMPACTION=false to disable the feature if unforeseen issues arise, but it will be removed in a future release.

Vulnerabilities in the xDS RBAC authorization engine and the HTTP/2 transport server implementation in google.golang.org/grpc

Authorization bypass in gRPC-Go via missing leading slash in :path in google.golang.org/grpc

A vulnerability exists in gRPC-Go servers configured with xds.NewGRPCServer() where a crafted request missing both :authority and Host headers can cause a server panic, resulting in a Denial of Service (DoS).

Servers built with xds.NewGRPCServer install an xDS routing interceptor on every RPC. This interceptor looks up the request’s :authority header to pick a virtual host. The HTTP/2 server transport previously accepted requests that had neither :authority nor Host. When this happened, the xDS routing interceptor attempted to access the first element of an empty slice of authorities, leading to an index out of bounds panic. Since the per-RPC goroutine does not recover from panics, the entire server process would terminate.

This panic occurs in the interceptor pipeline, meaning the transport credentials handshake (TLS, mTLS, or ALTS) and HTTP/2 connection establishment must complete successfully before the crafted request can reach this logic.

• Insecure/Standard TLS: If the server permits insecure (plaintext) connections or standard credentials (where client certs are not checked), any unauthenticated remote attacker can trigger the crash.
• mTLS / ALTS: If strict transport-level authentication is enforced at the network edge or transport layer (e.g., requiring a valid client certificate), the attacker must possess valid transport credentials to initiate the stream and trigger the panic.

Impact

An attacker can cause a complete outage of the gRPC server by sending a request missing both :authority and Host headers, provided they can successfully establish a transport connection.

Patches

The issue has been addressed in master (and backported to 1.83.2 and 1.82.2). The fix updates the HTTP/2 transport layer to reject requests missing both :authority and Host headers early, maintaining consistency with and other gRPC language implementations.

Summary

A vulnerability in the xDS RBAC HTTP filter implementation in grpc-go allows remote attackers to bypass authorization policies (specifically DENY rules) by using mixed-case or canonical-case header matchers (e.g., X-Role instead of x-role). Additionally, the safety guards introduced by gRFC A41 to block grpc- prefixed headers can be evaded via variations in casing (e.g., Grpc-Status).

Impact

When an operator defines an RBAC policy referencing headers containing uppercase letters (e.g. X-Role), grpc-go fails to match incoming metadata keys because they are unconditionally lowercased. Because of this case-sensitivity mismatch, a policy designed to block requests containing specific header values fails open: the rule is evaluated as a non-match, and traffic that should have been rejected is served.

Furthermore, gRFC A41 requires rejecting configuration schemas specifying header matchers starting with grpc-. Because this check is executed case-sensitively in grpc-go, attackers can bypass the validation by specifying titles like Grpc-Status.

Patches

The problem is fixed in master and in the 1.83.1 release.

Impact

An unauthenticated remote attacker can initiate a gRPC stream and purposefully fragment their payload into millions of tiny (e.g., 1-byte) HTTP/2 DATA frames. Even if the total payload volume falls within the configured connection and stream flow-control windows, each independent fragment incurs memory overhead due to internal tracking structures and queue allocation.

Repeated fragmentation massively inflates the heap space consumed by the stream. An attacker multiplexing multiple concurrent streams can exhaust the memory bounds of the runtime, forcing a runtime panic or OutOfMemory condition and leading to a remote Denial of Service (DoS).

Patches

The change to fix this issue is merged in master and a patch release, 1.83.1, has been published that contains this fix.

Workarounds

This vulnerability is mitigated by implementing receive buffer compaction. Consecutive small data buffers are automatically coalesced into larger buffers from a shared pool once the overhead is perceived to be excessive relative to actual payload data, drastically minimizing per-frame memory overheads.

This behavior is enabled by default. A temporary escape hatch is provided via the environment variable GRPC_GO_EXPERIMENTAL_ENABLE_RECEIVE_BUFFER_COMPACTION=false to disable the feature if unforeseen issues arise, but it will be removed in a future release.

Vulnerabilities in the xDS RBAC authorization engine and the HTTP/2 transport server implementation in google.golang.org/grpc

Authorization bypass in gRPC-Go via missing leading slash in :path in google.golang.org/grpc

A vulnerability exists in gRPC-Go servers configured with xds.NewGRPCServer() where a crafted request missing both :authority and Host headers can cause a server panic, resulting in a Denial of Service (DoS).

Servers built with xds.NewGRPCServer install an xDS routing interceptor on every RPC. This interceptor looks up the request’s :authority header to pick a virtual host. The HTTP/2 server transport previously accepted requests that had neither :authority nor Host. When this happened, the xDS routing interceptor attempted to access the first element of an empty slice of authorities, leading to an index out of bounds panic. Since the per-RPC goroutine does not recover from panics, the entire server process would terminate.

This panic occurs in the interceptor pipeline, meaning the transport credentials handshake (TLS, mTLS, or ALTS) and HTTP/2 connection establishment must complete successfully before the crafted request can reach this logic.

• Insecure/Standard TLS: If the server permits insecure (plaintext) connections or standard credentials (where client certs are not checked), any unauthenticated remote attacker can trigger the crash.
• mTLS / ALTS: If strict transport-level authentication is enforced at the network edge or transport layer (e.g., requiring a valid client certificate), the attacker must possess valid transport credentials to initiate the stream and trigger the panic.

Impact

An attacker can cause a complete outage of the gRPC server by sending a request missing both :authority and Host headers, provided they can successfully establish a transport connection.

Patches

The issue has been addressed in master (and backported to 1.83.2 and 1.82.2). The fix updates the HTTP/2 transport layer to reject requests missing both :authority and Host headers early, maintaining consistency with and other gRPC language implementations.

Summary

A vulnerability in the xDS RBAC HTTP filter implementation in grpc-go allows remote attackers to bypass authorization policies (specifically DENY rules) by using mixed-case or canonical-case header matchers (e.g., X-Role instead of x-role). Additionally, the safety guards introduced by gRFC A41 to block grpc- prefixed headers can be evaded via variations in casing (e.g., Grpc-Status).

Impact

When an operator defines an RBAC policy referencing headers containing uppercase letters (e.g. X-Role), grpc-go fails to match incoming metadata keys because they are unconditionally lowercased. Because of this case-sensitivity mismatch, a policy designed to block requests containing specific header values fails open: the rule is evaluated as a non-match, and traffic that should have been rejected is served.

Furthermore, gRFC A41 requires rejecting configuration schemas specifying header matchers starting with grpc-. Because this check is executed case-sensitively in grpc-go, attackers can bypass the validation by specifying titles like Grpc-Status.

Patches

The problem is fixed in master and in the 1.83.1 release.

Impact

An unauthenticated remote attacker can initiate a gRPC stream and purposefully fragment their payload into millions of tiny (e.g., 1-byte) HTTP/2 DATA frames. Even if the total payload volume falls within the configured connection and stream flow-control windows, each independent fragment incurs memory overhead due to internal tracking structures and queue allocation.

Repeated fragmentation massively inflates the heap space consumed by the stream. An attacker multiplexing multiple concurrent streams can exhaust the memory bounds of the runtime, forcing a runtime panic or OutOfMemory condition and leading to a remote Denial of Service (DoS).

Patches

The change to fix this issue is merged in master and a patch release, 1.83.1, has been published that contains this fix.

Workarounds

This vulnerability is mitigated by implementing receive buffer compaction. Consecutive small data buffers are automatically coalesced into larger buffers from a shared pool once the overhead is perceived to be excessive relative to actual payload data, drastically minimizing per-frame memory overheads.

This behavior is enabled by default. A temporary escape hatch is provided via the environment variable GRPC_GO_EXPERIMENTAL_ENABLE_RECEIVE_BUFFER_COMPACTION=false to disable the feature if unforeseen issues arise, but it will be removed in a future release.

Vulnerabilities in the xDS RBAC authorization engine and the HTTP/2 transport server implementation in google.golang.org/grpc

Authorization bypass in gRPC-Go via missing leading slash in :path in google.golang.org/grpc

A vulnerability exists in gRPC-Go servers configured with xds.NewGRPCServer() where a crafted request missing both :authority and Host headers can cause a server panic, resulting in a Denial of Service (DoS).

Servers built with xds.NewGRPCServer install an xDS routing interceptor on every RPC. This interceptor looks up the request’s :authority header to pick a virtual host. The HTTP/2 server transport previously accepted requests that had neither :authority nor Host. When this happened, the xDS routing interceptor attempted to access the first element of an empty slice of authorities, leading to an index out of bounds panic. Since the per-RPC goroutine does not recover from panics, the entire server process would terminate.

This panic occurs in the interceptor pipeline, meaning the transport credentials handshake (TLS, mTLS, or ALTS) and HTTP/2 connection establishment must complete successfully before the crafted request can reach this logic.

• Insecure/Standard TLS: If the server permits insecure (plaintext) connections or standard credentials (where client certs are not checked), any unauthenticated remote attacker can trigger the crash.
• mTLS / ALTS: If strict transport-level authentication is enforced at the network edge or transport layer (e.g., requiring a valid client certificate), the attacker must possess valid transport credentials to initiate the stream and trigger the panic.

Impact

An attacker can cause a complete outage of the gRPC server by sending a request missing both :authority and Host headers, provided they can successfully establish a transport connection.

Patches

The issue has been addressed in master (and backported to 1.83.2 and 1.82.2). The fix updates the HTTP/2 transport layer to reject requests missing both :authority and Host headers early, maintaining consistency with and other gRPC language implementations.

Summary

A vulnerability in the xDS RBAC HTTP filter implementation in grpc-go allows remote attackers to bypass authorization policies (specifically DENY rules) by using mixed-case or canonical-case header matchers (e.g., X-Role instead of x-role). Additionally, the safety guards introduced by gRFC A41 to block grpc- prefixed headers can be evaded via variations in casing (e.g., Grpc-Status).

Impact

When an operator defines an RBAC policy referencing headers containing uppercase letters (e.g. X-Role), grpc-go fails to match incoming metadata keys because they are unconditionally lowercased. Because of this case-sensitivity mismatch, a policy designed to block requests containing specific header values fails open: the rule is evaluated as a non-match, and traffic that should have been rejected is served.

Furthermore, gRFC A41 requires rejecting configuration schemas specifying header matchers starting with grpc-. Because this check is executed case-sensitively in grpc-go, attackers can bypass the validation by specifying titles like Grpc-Status.

Patches

The problem is fixed in master and in the 1.83.1 release.

Impact

An unauthenticated remote attacker can initiate a gRPC stream and purposefully fragment their payload into millions of tiny (e.g., 1-byte) HTTP/2 DATA frames. Even if the total payload volume falls within the configured connection and stream flow-control windows, each independent fragment incurs memory overhead due to internal tracking structures and queue allocation.

Repeated fragmentation massively inflates the heap space consumed by the stream. An attacker multiplexing multiple concurrent streams can exhaust the memory bounds of the runtime, forcing a runtime panic or OutOfMemory condition and leading to a remote Denial of Service (DoS).

Patches

The change to fix this issue is merged in master and a patch release, 1.83.1, has been published that contains this fix.

Workarounds

This vulnerability is mitigated by implementing receive buffer compaction. Consecutive small data buffers are automatically coalesced into larger buffers from a shared pool once the overhead is perceived to be excessive relative to actual payload data, drastically minimizing per-frame memory overheads.

This behavior is enabled by default. A temporary escape hatch is provided via the environment variable GRPC_GO_EXPERIMENTAL_ENABLE_RECEIVE_BUFFER_COMPACTION=false to disable the feature if unforeseen issues arise, but it will be removed in a future release.

Vulnerabilities in the xDS RBAC authorization engine and the HTTP/2 transport server implementation in google.golang.org/grpc

A vulnerability exists in gRPC-Go servers configured with xds.NewGRPCServer() where a crafted request missing both :authority and Host headers can cause a server panic, resulting in a Denial of Service (DoS).

Servers built with xds.NewGRPCServer install an xDS routing interceptor on every RPC. This interceptor looks up the request’s :authority header to pick a virtual host. The HTTP/2 server transport previously accepted requests that had neither :authority nor Host. When this happened, the xDS routing interceptor attempted to access the first element of an empty slice of authorities, leading to an index out of bounds panic. Since the per-RPC goroutine does not recover from panics, the entire server process would terminate.

This panic occurs in the interceptor pipeline, meaning the transport credentials handshake (TLS, mTLS, or ALTS) and HTTP/2 connection establishment must complete successfully before the crafted request can reach this logic.

• Insecure/Standard TLS: If the server permits insecure (plaintext) connections or standard credentials (where client certs are not checked), any unauthenticated remote attacker can trigger the crash.
• mTLS / ALTS: If strict transport-level authentication is enforced at the network edge or transport layer (e.g., requiring a valid client certificate), the attacker must possess valid transport credentials to initiate the stream and trigger the panic.

Impact

An attacker can cause a complete outage of the gRPC server by sending a request missing both :authority and Host headers, provided they can successfully establish a transport connection.

Patches

The issue has been addressed in master (and backported to 1.83.2 and 1.82.2). The fix updates the HTTP/2 transport layer to reject requests missing both :authority and Host headers early, maintaining consistency with and other gRPC language implementations.

Summary

A vulnerability in the xDS RBAC HTTP filter implementation in grpc-go allows remote attackers to bypass authorization policies (specifically DENY rules) by using mixed-case or canonical-case header matchers (e.g., X-Role instead of x-role). Additionally, the safety guards introduced by gRFC A41 to block grpc- prefixed headers can be evaded via variations in casing (e.g., Grpc-Status).

Impact

When an operator defines an RBAC policy referencing headers containing uppercase letters (e.g. X-Role), grpc-go fails to match incoming metadata keys because they are unconditionally lowercased. Because of this case-sensitivity mismatch, a policy designed to block requests containing specific header values fails open: the rule is evaluated as a non-match, and traffic that should have been rejected is served.

Furthermore, gRFC A41 requires rejecting configuration schemas specifying header matchers starting with grpc-. Because this check is executed case-sensitively in grpc-go, attackers can bypass the validation by specifying titles like Grpc-Status.

Patches

The problem is fixed in master and in the 1.83.1 release.

Impact

An unauthenticated remote attacker can initiate a gRPC stream and purposefully fragment their payload into millions of tiny (e.g., 1-byte) HTTP/2 DATA frames. Even if the total payload volume falls within the configured connection and stream flow-control windows, each independent fragment incurs memory overhead due to internal tracking structures and queue allocation.

Repeated fragmentation massively inflates the heap space consumed by the stream. An attacker multiplexing multiple concurrent streams can exhaust the memory bounds of the runtime, forcing a runtime panic or OutOfMemory condition and leading to a remote Denial of Service (DoS).

Patches

The change to fix this issue is merged in master and a patch release, 1.83.1, has been published that contains this fix.

Workarounds

This vulnerability is mitigated by implementing receive buffer compaction. Consecutive small data buffers are automatically coalesced into larger buffers from a shared pool once the overhead is perceived to be excessive relative to actual payload data, drastically minimizing per-frame memory overheads.

This behavior is enabled by default. A temporary escape hatch is provided via the environment variable GRPC_GO_EXPERIMENTAL_ENABLE_RECEIVE_BUFFER_COMPACTION=false to disable the feature if unforeseen issues arise, but it will be removed in a future release.

Vulnerabilities in the xDS RBAC authorization engine and the HTTP/2 transport server implementation in google.golang.org/grpc

Authorization bypass in gRPC-Go via missing leading slash in :path in google.golang.org/grpc

A vulnerability exists in gRPC-Go servers configured with xds.NewGRPCServer() where a crafted request missing both :authority and Host headers can cause a server panic, resulting in a Denial of Service (DoS).

Servers built with xds.NewGRPCServer install an xDS routing interceptor on every RPC. This interceptor looks up the request’s :authority header to pick a virtual host. The HTTP/2 server transport previously accepted requests that had neither :authority nor Host. When this happened, the xDS routing interceptor attempted to access the first element of an empty slice of authorities, leading to an index out of bounds panic. Since the per-RPC goroutine does not recover from panics, the entire server process would terminate.

This panic occurs in the interceptor pipeline, meaning the transport credentials handshake (TLS, mTLS, or ALTS) and HTTP/2 connection establishment must complete successfully before the crafted request can reach this logic.

• Insecure/Standard TLS: If the server permits insecure (plaintext) connections or standard credentials (where client certs are not checked), any unauthenticated remote attacker can trigger the crash.
• mTLS / ALTS: If strict transport-level authentication is enforced at the network edge or transport layer (e.g., requiring a valid client certificate), the attacker must possess valid transport credentials to initiate the stream and trigger the panic.

Impact

An attacker can cause a complete outage of the gRPC server by sending a request missing both :authority and Host headers, provided they can successfully establish a transport connection.

Patches

The issue has been addressed in master (and backported to 1.83.2 and 1.82.2). The fix updates the HTTP/2 transport layer to reject requests missing both :authority and Host headers early, maintaining consistency with and other gRPC language implementations.

Summary

A vulnerability in the xDS RBAC HTTP filter implementation in grpc-go allows remote attackers to bypass authorization policies (specifically DENY rules) by using mixed-case or canonical-case header matchers (e.g., X-Role instead of x-role). Additionally, the safety guards introduced by gRFC A41 to block grpc- prefixed headers can be evaded via variations in casing (e.g., Grpc-Status).

Impact

When an operator defines an RBAC policy referencing headers containing uppercase letters (e.g. X-Role), grpc-go fails to match incoming metadata keys because they are unconditionally lowercased. Because of this case-sensitivity mismatch, a policy designed to block requests containing specific header values fails open: the rule is evaluated as a non-match, and traffic that should have been rejected is served.

Furthermore, gRFC A41 requires rejecting configuration schemas specifying header matchers starting with grpc-. Because this check is executed case-sensitively in grpc-go, attackers can bypass the validation by specifying titles like Grpc-Status.

Patches

The problem is fixed in master and in the 1.83.1 release.

Impact

An unauthenticated remote attacker can initiate a gRPC stream and purposefully fragment their payload into millions of tiny (e.g., 1-byte) HTTP/2 DATA frames. Even if the total payload volume falls within the configured connection and stream flow-control windows, each independent fragment incurs memory overhead due to internal tracking structures and queue allocation.

Repeated fragmentation massively inflates the heap space consumed by the stream. An attacker multiplexing multiple concurrent streams can exhaust the memory bounds of the runtime, forcing a runtime panic or OutOfMemory condition and leading to a remote Denial of Service (DoS).

Patches

The change to fix this issue is merged in master and a patch release, 1.83.1, has been published that contains this fix.

Workarounds

This vulnerability is mitigated by implementing receive buffer compaction. Consecutive small data buffers are automatically coalesced into larger buffers from a shared pool once the overhead is perceived to be excessive relative to actual payload data, drastically minimizing per-frame memory overheads.

This behavior is enabled by default. A temporary escape hatch is provided via the environment variable GRPC_GO_EXPERIMENTAL_ENABLE_RECEIVE_BUFFER_COMPACTION=false to disable the feature if unforeseen issues arise, but it will be removed in a future release.

Vulnerabilities in the xDS RBAC authorization engine and the HTTP/2 transport server implementation in google.golang.org/grpc

Authorization bypass in gRPC-Go via missing leading slash in :path in google.golang.org/grpc

A vulnerability exists in gRPC-Go servers configured with xds.NewGRPCServer() where a crafted request missing both :authority and Host headers can cause a server panic, resulting in a Denial of Service (DoS).

Servers built with xds.NewGRPCServer install an xDS routing interceptor on every RPC. This interceptor looks up the request’s :authority header to pick a virtual host. The HTTP/2 server transport previously accepted requests that had neither :authority nor Host. When this happened, the xDS routing interceptor attempted to access the first element of an empty slice of authorities, leading to an index out of bounds panic. Since the per-RPC goroutine does not recover from panics, the entire server process would terminate.

This panic occurs in the interceptor pipeline, meaning the transport credentials handshake (TLS, mTLS, or ALTS) and HTTP/2 connection establishment must complete successfully before the crafted request can reach this logic.

• Insecure/Standard TLS: If the server permits insecure (plaintext) connections or standard credentials (where client certs are not checked), any unauthenticated remote attacker can trigger the crash.
• mTLS / ALTS: If strict transport-level authentication is enforced at the network edge or transport layer (e.g., requiring a valid client certificate), the attacker must possess valid transport credentials to initiate the stream and trigger the panic.

Impact

An attacker can cause a complete outage of the gRPC server by sending a request missing both :authority and Host headers, provided they can successfully establish a transport connection.

Patches

The issue has been addressed in master (and backported to 1.83.2 and 1.82.2). The fix updates the HTTP/2 transport layer to reject requests missing both :authority and Host headers early, maintaining consistency with and other gRPC language implementations.

Summary

A vulnerability in the xDS RBAC HTTP filter implementation in grpc-go allows remote attackers to bypass authorization policies (specifically DENY rules) by using mixed-case or canonical-case header matchers (e.g., X-Role instead of x-role). Additionally, the safety guards introduced by gRFC A41 to block grpc- prefixed headers can be evaded via variations in casing (e.g., Grpc-Status).

Impact

When an operator defines an RBAC policy referencing headers containing uppercase letters (e.g. X-Role), grpc-go fails to match incoming metadata keys because they are unconditionally lowercased. Because of this case-sensitivity mismatch, a policy designed to block requests containing specific header values fails open: the rule is evaluated as a non-match, and traffic that should have been rejected is served.

Furthermore, gRFC A41 requires rejecting configuration schemas specifying header matchers starting with grpc-. Because this check is executed case-sensitively in grpc-go, attackers can bypass the validation by specifying titles like Grpc-Status.

Patches

The problem is fixed in master and in the 1.83.1 release.

Impact

An unauthenticated remote attacker can initiate a gRPC stream and purposefully fragment their payload into millions of tiny (e.g., 1-byte) HTTP/2 DATA frames. Even if the total payload volume falls within the configured connection and stream flow-control windows, each independent fragment incurs memory overhead due to internal tracking structures and queue allocation.

Repeated fragmentation massively inflates the heap space consumed by the stream. An attacker multiplexing multiple concurrent streams can exhaust the memory bounds of the runtime, forcing a runtime panic or OutOfMemory condition and leading to a remote Denial of Service (DoS).

Patches

The change to fix this issue is merged in master and a patch release, 1.83.1, has been published that contains this fix.

Workarounds

This vulnerability is mitigated by implementing receive buffer compaction. Consecutive small data buffers are automatically coalesced into larger buffers from a shared pool once the overhead is perceived to be excessive relative to actual payload data, drastically minimizing per-frame memory overheads.

This behavior is enabled by default. A temporary escape hatch is provided via the environment variable GRPC_GO_EXPERIMENTAL_ENABLE_RECEIVE_BUFFER_COMPACTION=false to disable the feature if unforeseen issues arise, but it will be removed in a future release.

Vulnerabilities in the xDS RBAC authorization engine and the HTTP/2 transport server implementation in google.golang.org/grpc

Authorization bypass in gRPC-Go via missing leading slash in :path in google.golang.org/grpc

A vulnerability exists in gRPC-Go servers configured with xds.NewGRPCServer() where a crafted request missing both :authority and Host headers can cause a server panic, resulting in a Denial of Service (DoS).

Servers built with xds.NewGRPCServer install an xDS routing interceptor on every RPC. This interceptor looks up the request’s :authority header to pick a virtual host. The HTTP/2 server transport previously accepted requests that had neither :authority nor Host. When this happened, the xDS routing interceptor attempted to access the first element of an empty slice of authorities, leading to an index out of bounds panic. Since the per-RPC goroutine does not recover from panics, the entire server process would terminate.

This panic occurs in the interceptor pipeline, meaning the transport credentials handshake (TLS, mTLS, or ALTS) and HTTP/2 connection establishment must complete successfully before the crafted request can reach this logic.

• Insecure/Standard TLS: If the server permits insecure (plaintext) connections or standard credentials (where client certs are not checked), any unauthenticated remote attacker can trigger the crash.
• mTLS / ALTS: If strict transport-level authentication is enforced at the network edge or transport layer (e.g., requiring a valid client certificate), the attacker must possess valid transport credentials to initiate the stream and trigger the panic.

Impact

An attacker can cause a complete outage of the gRPC server by sending a request missing both :authority and Host headers, provided they can successfully establish a transport connection.

Patches

The issue has been addressed in master (and backported to 1.83.2 and 1.82.2). The fix updates the HTTP/2 transport layer to reject requests missing both :authority and Host headers early, maintaining consistency with and other gRPC language implementations.

Summary

A vulnerability in the xDS RBAC HTTP filter implementation in grpc-go allows remote attackers to bypass authorization policies (specifically DENY rules) by using mixed-case or canonical-case header matchers (e.g., X-Role instead of x-role). Additionally, the safety guards introduced by gRFC A41 to block grpc- prefixed headers can be evaded via variations in casing (e.g., Grpc-Status).

Impact

When an operator defines an RBAC policy referencing headers containing uppercase letters (e.g. X-Role), grpc-go fails to match incoming metadata keys because they are unconditionally lowercased. Because of this case-sensitivity mismatch, a policy designed to block requests containing specific header values fails open: the rule is evaluated as a non-match, and traffic that should have been rejected is served.

Furthermore, gRFC A41 requires rejecting configuration schemas specifying header matchers starting with grpc-. Because this check is executed case-sensitively in grpc-go, attackers can bypass the validation by specifying titles like Grpc-Status.

Patches

The problem is fixed in master and in the 1.83.1 release.

Impact

An unauthenticated remote attacker can initiate a gRPC stream and purposefully fragment their payload into millions of tiny (e.g., 1-byte) HTTP/2 DATA frames. Even if the total payload volume falls within the configured connection and stream flow-control windows, each independent fragment incurs memory overhead due to internal tracking structures and queue allocation.

Repeated fragmentation massively inflates the heap space consumed by the stream. An attacker multiplexing multiple concurrent streams can exhaust the memory bounds of the runtime, forcing a runtime panic or OutOfMemory condition and leading to a remote Denial of Service (DoS).

Patches

The change to fix this issue is merged in master and a patch release, 1.83.1, has been published that contains this fix.

Workarounds

This vulnerability is mitigated by implementing receive buffer compaction. Consecutive small data buffers are automatically coalesced into larger buffers from a shared pool once the overhead is perceived to be excessive relative to actual payload data, drastically minimizing per-frame memory overheads.

This behavior is enabled by default. A temporary escape hatch is provided via the environment variable GRPC_GO_EXPERIMENTAL_ENABLE_RECEIVE_BUFFER_COMPACTION=false to disable the feature if unforeseen issues arise, but it will be removed in a future release.

Vulnerabilities in the xDS RBAC authorization engine and the HTTP/2 transport server implementation in google.golang.org/grpc

Authorization bypass in gRPC-Go via missing leading slash in :path in google.golang.org/grpc

A vulnerability exists in gRPC-Go servers configured with xds.NewGRPCServer() where a crafted request missing both :authority and Host headers can cause a server panic, resulting in a Denial of Service (DoS).

Servers built with xds.NewGRPCServer install an xDS routing interceptor on every RPC. This interceptor looks up the request’s :authority header to pick a virtual host. The HTTP/2 server transport previously accepted requests that had neither :authority nor Host. When this happened, the xDS routing interceptor attempted to access the first element of an empty slice of authorities, leading to an index out of bounds panic. Since the per-RPC goroutine does not recover from panics, the entire server process would terminate.

This panic occurs in the interceptor pipeline, meaning the transport credentials handshake (TLS, mTLS, or ALTS) and HTTP/2 connection establishment must complete successfully before the crafted request can reach this logic.

• Insecure/Standard TLS: If the server permits insecure (plaintext) connections or standard credentials (where client certs are not checked), any unauthenticated remote attacker can trigger the crash.
• mTLS / ALTS: If strict transport-level authentication is enforced at the network edge or transport layer (e.g., requiring a valid client certificate), the attacker must possess valid transport credentials to initiate the stream and trigger the panic.

Impact

An attacker can cause a complete outage of the gRPC server by sending a request missing both :authority and Host headers, provided they can successfully establish a transport connection.

Patches

The issue has been addressed in master (and backported to 1.83.2 and 1.82.2). The fix updates the HTTP/2 transport layer to reject requests missing both :authority and Host headers early, maintaining consistency with and other gRPC language implementations.

Summary

A vulnerability in the xDS RBAC HTTP filter implementation in grpc-go allows remote attackers to bypass authorization policies (specifically DENY rules) by using mixed-case or canonical-case header matchers (e.g., X-Role instead of x-role). Additionally, the safety guards introduced by gRFC A41 to block grpc- prefixed headers can be evaded via variations in casing (e.g., Grpc-Status).

Impact

When an operator defines an RBAC policy referencing headers containing uppercase letters (e.g. X-Role), grpc-go fails to match incoming metadata keys because they are unconditionally lowercased. Because of this case-sensitivity mismatch, a policy designed to block requests containing specific header values fails open: the rule is evaluated as a non-match, and traffic that should have been rejected is served.

Furthermore, gRFC A41 requires rejecting configuration schemas specifying header matchers starting with grpc-. Because this check is executed case-sensitively in grpc-go, attackers can bypass the validation by specifying titles like Grpc-Status.

Patches

The problem is fixed in master and in the 1.83.1 release.

Impact

An unauthenticated remote attacker can initiate a gRPC stream and purposefully fragment their payload into millions of tiny (e.g., 1-byte) HTTP/2 DATA frames. Even if the total payload volume falls within the configured connection and stream flow-control windows, each independent fragment incurs memory overhead due to internal tracking structures and queue allocation.

Repeated fragmentation massively inflates the heap space consumed by the stream. An attacker multiplexing multiple concurrent streams can exhaust the memory bounds of the runtime, forcing a runtime panic or OutOfMemory condition and leading to a remote Denial of Service (DoS).

Patches

The change to fix this issue is merged in master and a patch release, 1.83.1, has been published that contains this fix.

Workarounds

This vulnerability is mitigated by implementing receive buffer compaction. Consecutive small data buffers are automatically coalesced into larger buffers from a shared pool once the overhead is perceived to be excessive relative to actual payload data, drastically minimizing per-frame memory overheads.

This behavior is enabled by default. A temporary escape hatch is provided via the environment variable GRPC_GO_EXPERIMENTAL_ENABLE_RECEIVE_BUFFER_COMPACTION=false to disable the feature if unforeseen issues arise, but it will be removed in a future release.

Vulnerabilities in the xDS RBAC authorization engine and the HTTP/2 transport server implementation in google.golang.org/grpc

Authorization bypass in gRPC-Go via missing leading slash in :path in google.golang.org/grpc

A vulnerability exists in gRPC-Go servers configured with xds.NewGRPCServer() where a crafted request missing both :authority and Host headers can cause a server panic, resulting in a Denial of Service (DoS).

Servers built with xds.NewGRPCServer install an xDS routing interceptor on every RPC. This interceptor looks up the request’s :authority header to pick a virtual host. The HTTP/2 server transport previously accepted requests that had neither :authority nor Host. When this happened, the xDS routing interceptor attempted to access the first element of an empty slice of authorities, leading to an index out of bounds panic. Since the per-RPC goroutine does not recover from panics, the entire server process would terminate.

This panic occurs in the interceptor pipeline, meaning the transport credentials handshake (TLS, mTLS, or ALTS) and HTTP/2 connection establishment must complete successfully before the crafted request can reach this logic.

• Insecure/Standard TLS: If the server permits insecure (plaintext) connections or standard credentials (where client certs are not checked), any unauthenticated remote attacker can trigger the crash.
• mTLS / ALTS: If strict transport-level authentication is enforced at the network edge or transport layer (e.g., requiring a valid client certificate), the attacker must possess valid transport credentials to initiate the stream and trigger the panic.

Impact

An attacker can cause a complete outage of the gRPC server by sending a request missing both :authority and Host headers, provided they can successfully establish a transport connection.

Patches

The issue has been addressed in master (and backported to 1.83.2 and 1.82.2). The fix updates the HTTP/2 transport layer to reject requests missing both :authority and Host headers early, maintaining consistency with and other gRPC language implementations.

Summary

A vulnerability in the xDS RBAC HTTP filter implementation in grpc-go allows remote attackers to bypass authorization policies (specifically DENY rules) by using mixed-case or canonical-case header matchers (e.g., X-Role instead of x-role). Additionally, the safety guards introduced by gRFC A41 to block grpc- prefixed headers can be evaded via variations in casing (e.g., Grpc-Status).

Impact

When an operator defines an RBAC policy referencing headers containing uppercase letters (e.g. X-Role), grpc-go fails to match incoming metadata keys because they are unconditionally lowercased. Because of this case-sensitivity mismatch, a policy designed to block requests containing specific header values fails open: the rule is evaluated as a non-match, and traffic that should have been rejected is served.

Furthermore, gRFC A41 requires rejecting configuration schemas specifying header matchers starting with grpc-. Because this check is executed case-sensitively in grpc-go, attackers can bypass the validation by specifying titles like Grpc-Status.

Patches

The problem is fixed in master and in the 1.83.1 release.

Impact

An unauthenticated remote attacker can initiate a gRPC stream and purposefully fragment their payload into millions of tiny (e.g., 1-byte) HTTP/2 DATA frames. Even if the total payload volume falls within the configured connection and stream flow-control windows, each independent fragment incurs memory overhead due to internal tracking structures and queue allocation.

Repeated fragmentation massively inflates the heap space consumed by the stream. An attacker multiplexing multiple concurrent streams can exhaust the memory bounds of the runtime, forcing a runtime panic or OutOfMemory condition and leading to a remote Denial of Service (DoS).

Patches

The change to fix this issue is merged in master and a patch release, 1.83.1, has been published that contains this fix.

Workarounds

This vulnerability is mitigated by implementing receive buffer compaction. Consecutive small data buffers are automatically coalesced into larger buffers from a shared pool once the overhead is perceived to be excessive relative to actual payload data, drastically minimizing per-frame memory overheads.

This behavior is enabled by default. A temporary escape hatch is provided via the environment variable GRPC_GO_EXPERIMENTAL_ENABLE_RECEIVE_BUFFER_COMPACTION=false to disable the feature if unforeseen issues arise, but it will be removed in a future release.

Vulnerabilities in the xDS RBAC authorization engine and the HTTP/2 transport server implementation in google.golang.org/grpc

Authorization bypass in gRPC-Go via missing leading slash in :path in google.golang.org/grpc

A vulnerability exists in gRPC-Go servers configured with xds.NewGRPCServer() where a crafted request missing both :authority and Host headers can cause a server panic, resulting in a Denial of Service (DoS).

Servers built with xds.NewGRPCServer install an xDS routing interceptor on every RPC. This interceptor looks up the request’s :authority header to pick a virtual host. The HTTP/2 server transport previously accepted requests that had neither :authority nor Host. When this happened, the xDS routing interceptor attempted to access the first element of an empty slice of authorities, leading to an index out of bounds panic. Since the per-RPC goroutine does not recover from panics, the entire server process would terminate.

This panic occurs in the interceptor pipeline, meaning the transport credentials handshake (TLS, mTLS, or ALTS) and HTTP/2 connection establishment must complete successfully before the crafted request can reach this logic.

• Insecure/Standard TLS: If the server permits insecure (plaintext) connections or standard credentials (where client certs are not checked), any unauthenticated remote attacker can trigger the crash.
• mTLS / ALTS: If strict transport-level authentication is enforced at the network edge or transport layer (e.g., requiring a valid client certificate), the attacker must possess valid transport credentials to initiate the stream and trigger the panic.

Impact

An attacker can cause a complete outage of the gRPC server by sending a request missing both :authority and Host headers, provided they can successfully establish a transport connection.

Patches

The issue has been addressed in master (and backported to 1.83.2 and 1.82.2). The fix updates the HTTP/2 transport layer to reject requests missing both :authority and Host headers early, maintaining consistency with and other gRPC language implementations.

Summary

A vulnerability in the xDS RBAC HTTP filter implementation in grpc-go allows remote attackers to bypass authorization policies (specifically DENY rules) by using mixed-case or canonical-case header matchers (e.g., X-Role instead of x-role). Additionally, the safety guards introduced by gRFC A41 to block grpc- prefixed headers can be evaded via variations in casing (e.g., Grpc-Status).

Impact

When an operator defines an RBAC policy referencing headers containing uppercase letters (e.g. X-Role), grpc-go fails to match incoming metadata keys because they are unconditionally lowercased. Because of this case-sensitivity mismatch, a policy designed to block requests containing specific header values fails open: the rule is evaluated as a non-match, and traffic that should have been rejected is served.

Furthermore, gRFC A41 requires rejecting configuration schemas specifying header matchers starting with grpc-. Because this check is executed case-sensitively in grpc-go, attackers can bypass the validation by specifying titles like Grpc-Status.

Patches

The problem is fixed in master and in the 1.83.1 release.

Impact

An unauthenticated remote attacker can initiate a gRPC stream and purposefully fragment their payload into millions of tiny (e.g., 1-byte) HTTP/2 DATA frames. Even if the total payload volume falls within the configured connection and stream flow-control windows, each independent fragment incurs memory overhead due to internal tracking structures and queue allocation.

Repeated fragmentation massively inflates the heap space consumed by the stream. An attacker multiplexing multiple concurrent streams can exhaust the memory bounds of the runtime, forcing a runtime panic or OutOfMemory condition and leading to a remote Denial of Service (DoS).

Patches

The change to fix this issue is merged in master and a patch release, 1.83.1, has been published that contains this fix.

Workarounds

This vulnerability is mitigated by implementing receive buffer compaction. Consecutive small data buffers are automatically coalesced into larger buffers from a shared pool once the overhead is perceived to be excessive relative to actual payload data, drastically minimizing per-frame memory overheads.

This behavior is enabled by default. A temporary escape hatch is provided via the environment variable GRPC_GO_EXPERIMENTAL_ENABLE_RECEIVE_BUFFER_COMPACTION=false to disable the feature if unforeseen issues arise, but it will be removed in a future release.

Vulnerabilities in the xDS RBAC authorization engine and the HTTP/2 transport server implementation in google.golang.org/grpc

Authorization bypass in gRPC-Go via missing leading slash in :path in google.golang.org/grpc

A vulnerability exists in gRPC-Go servers configured with xds.NewGRPCServer() where a crafted request missing both :authority and Host headers can cause a server panic, resulting in a Denial of Service (DoS).

Servers built with xds.NewGRPCServer install an xDS routing interceptor on every RPC. This interceptor looks up the request’s :authority header to pick a virtual host. The HTTP/2 server transport previously accepted requests that had neither :authority nor Host. When this happened, the xDS routing interceptor attempted to access the first element of an empty slice of authorities, leading to an index out of bounds panic. Since the per-RPC goroutine does not recover from panics, the entire server process would terminate.

This panic occurs in the interceptor pipeline, meaning the transport credentials handshake (TLS, mTLS, or ALTS) and HTTP/2 connection establishment must complete successfully before the crafted request can reach this logic.

• Insecure/Standard TLS: If the server permits insecure (plaintext) connections or standard credentials (where client certs are not checked), any unauthenticated remote attacker can trigger the crash.
• mTLS / ALTS: If strict transport-level authentication is enforced at the network edge or transport layer (e.g., requiring a valid client certificate), the attacker must possess valid transport credentials to initiate the stream and trigger the panic.

Impact

An attacker can cause a complete outage of the gRPC server by sending a request missing both :authority and Host headers, provided they can successfully establish a transport connection.

Patches

The issue has been addressed in master (and backported to 1.83.2 and 1.82.2). The fix updates the HTTP/2 transport layer to reject requests missing both :authority and Host headers early, maintaining consistency with and other gRPC language implementations.

Summary

A vulnerability in the xDS RBAC HTTP filter implementation in grpc-go allows remote attackers to bypass authorization policies (specifically DENY rules) by using mixed-case or canonical-case header matchers (e.g., X-Role instead of x-role). Additionally, the safety guards introduced by gRFC A41 to block grpc- prefixed headers can be evaded via variations in casing (e.g., Grpc-Status).

Impact

When an operator defines an RBAC policy referencing headers containing uppercase letters (e.g. X-Role), grpc-go fails to match incoming metadata keys because they are unconditionally lowercased. Because of this case-sensitivity mismatch, a policy designed to block requests containing specific header values fails open: the rule is evaluated as a non-match, and traffic that should have been rejected is served.

Furthermore, gRFC A41 requires rejecting configuration schemas specifying header matchers starting with grpc-. Because this check is executed case-sensitively in grpc-go, attackers can bypass the validation by specifying titles like Grpc-Status.

Patches

The problem is fixed in master and in the 1.83.1 release.

Impact

An unauthenticated remote attacker can initiate a gRPC stream and purposefully fragment their payload into millions of tiny (e.g., 1-byte) HTTP/2 DATA frames. Even if the total payload volume falls within the configured connection and stream flow-control windows, each independent fragment incurs memory overhead due to internal tracking structures and queue allocation.

Repeated fragmentation massively inflates the heap space consumed by the stream. An attacker multiplexing multiple concurrent streams can exhaust the memory bounds of the runtime, forcing a runtime panic or OutOfMemory condition and leading to a remote Denial of Service (DoS).

Patches

The change to fix this issue is merged in master and a patch release, 1.83.1, has been published that contains this fix.

Workarounds

This vulnerability is mitigated by implementing receive buffer compaction. Consecutive small data buffers are automatically coalesced into larger buffers from a shared pool once the overhead is perceived to be excessive relative to actual payload data, drastically minimizing per-frame memory overheads.

This behavior is enabled by default. A temporary escape hatch is provided via the environment variable GRPC_GO_EXPERIMENTAL_ENABLE_RECEIVE_BUFFER_COMPACTION=false to disable the feature if unforeseen issues arise, but it will be removed in a future release.

Vulnerabilities in the xDS RBAC authorization engine and the HTTP/2 transport server implementation in google.golang.org/grpc

Authorization bypass in gRPC-Go via missing leading slash in :path in google.golang.org/grpc

A vulnerability exists in gRPC-Go servers configured with xds.NewGRPCServer() where a crafted request missing both :authority and Host headers can cause a server panic, resulting in a Denial of Service (DoS).

Servers built with xds.NewGRPCServer install an xDS routing interceptor on every RPC. This interceptor looks up the request’s :authority header to pick a virtual host. The HTTP/2 server transport previously accepted requests that had neither :authority nor Host. When this happened, the xDS routing interceptor attempted to access the first element of an empty slice of authorities, leading to an index out of bounds panic. Since the per-RPC goroutine does not recover from panics, the entire server process would terminate.

This panic occurs in the interceptor pipeline, meaning the transport credentials handshake (TLS, mTLS, or ALTS) and HTTP/2 connection establishment must complete successfully before the crafted request can reach this logic.

• Insecure/Standard TLS: If the server permits insecure (plaintext) connections or standard credentials (where client certs are not checked), any unauthenticated remote attacker can trigger the crash.
• mTLS / ALTS: If strict transport-level authentication is enforced at the network edge or transport layer (e.g., requiring a valid client certificate), the attacker must possess valid transport credentials to initiate the stream and trigger the panic.

Impact

An attacker can cause a complete outage of the gRPC server by sending a request missing both :authority and Host headers, provided they can successfully establish a transport connection.

Patches

The issue has been addressed in master (and backported to 1.83.2 and 1.82.2). The fix updates the HTTP/2 transport layer to reject requests missing both :authority and Host headers early, maintaining consistency with and other gRPC language implementations.

Summary

A vulnerability in the xDS RBAC HTTP filter implementation in grpc-go allows remote attackers to bypass authorization policies (specifically DENY rules) by using mixed-case or canonical-case header matchers (e.g., X-Role instead of x-role). Additionally, the safety guards introduced by gRFC A41 to block grpc- prefixed headers can be evaded via variations in casing (e.g., Grpc-Status).

Impact

When an operator defines an RBAC policy referencing headers containing uppercase letters (e.g. X-Role), grpc-go fails to match incoming metadata keys because they are unconditionally lowercased. Because of this case-sensitivity mismatch, a policy designed to block requests containing specific header values fails open: the rule is evaluated as a non-match, and traffic that should have been rejected is served.

Furthermore, gRFC A41 requires rejecting configuration schemas specifying header matchers starting with grpc-. Because this check is executed case-sensitively in grpc-go, attackers can bypass the validation by specifying titles like Grpc-Status.

Patches

The problem is fixed in master and in the 1.83.1 release.

Impact

An unauthenticated remote attacker can initiate a gRPC stream and purposefully fragment their payload into millions of tiny (e.g., 1-byte) HTTP/2 DATA frames. Even if the total payload volume falls within the configured connection and stream flow-control windows, each independent fragment incurs memory overhead due to internal tracking structures and queue allocation.

Repeated fragmentation massively inflates the heap space consumed by the stream. An attacker multiplexing multiple concurrent streams can exhaust the memory bounds of the runtime, forcing a runtime panic or OutOfMemory condition and leading to a remote Denial of Service (DoS).

Patches

The change to fix this issue is merged in master and a patch release, 1.83.1, has been published that contains this fix.

Workarounds

This vulnerability is mitigated by implementing receive buffer compaction. Consecutive small data buffers are automatically coalesced into larger buffers from a shared pool once the overhead is perceived to be excessive relative to actual payload data, drastically minimizing per-frame memory overheads.

This behavior is enabled by default. A temporary escape hatch is provided via the environment variable GRPC_GO_EXPERIMENTAL_ENABLE_RECEIVE_BUFFER_COMPACTION=false to disable the feature if unforeseen issues arise, but it will be removed in a future release.

Vulnerabilities in the xDS RBAC authorization engine and the HTTP/2 transport server implementation in google.golang.org/grpc

Authorization bypass in gRPC-Go via missing leading slash in :path in google.golang.org/grpc

A vulnerability exists in gRPC-Go servers configured with xds.NewGRPCServer() where a crafted request missing both :authority and Host headers can cause a server panic, resulting in a Denial of Service (DoS).

Servers built with xds.NewGRPCServer install an xDS routing interceptor on every RPC. This interceptor looks up the request’s :authority header to pick a virtual host. The HTTP/2 server transport previously accepted requests that had neither :authority nor Host. When this happened, the xDS routing interceptor attempted to access the first element of an empty slice of authorities, leading to an index out of bounds panic. Since the per-RPC goroutine does not recover from panics, the entire server process would terminate.

This panic occurs in the interceptor pipeline, meaning the transport credentials handshake (TLS, mTLS, or ALTS) and HTTP/2 connection establishment must complete successfully before the crafted request can reach this logic.

• Insecure/Standard TLS: If the server permits insecure (plaintext) connections or standard credentials (where client certs are not checked), any unauthenticated remote attacker can trigger the crash.
• mTLS / ALTS: If strict transport-level authentication is enforced at the network edge or transport layer (e.g., requiring a valid client certificate), the attacker must possess valid transport credentials to initiate the stream and trigger the panic.

Impact

An attacker can cause a complete outage of the gRPC server by sending a request missing both :authority and Host headers, provided they can successfully establish a transport connection.

Patches

The issue has been addressed in master (and backported to 1.83.2 and 1.82.2). The fix updates the HTTP/2 transport layer to reject requests missing both :authority and Host headers early, maintaining consistency with and other gRPC language implementations.

Summary

A vulnerability in the xDS RBAC HTTP filter implementation in grpc-go allows remote attackers to bypass authorization policies (specifically DENY rules) by using mixed-case or canonical-case header matchers (e.g., X-Role instead of x-role). Additionally, the safety guards introduced by gRFC A41 to block grpc- prefixed headers can be evaded via variations in casing (e.g., Grpc-Status).

Impact

When an operator defines an RBAC policy referencing headers containing uppercase letters (e.g. X-Role), grpc-go fails to match incoming metadata keys because they are unconditionally lowercased. Because of this case-sensitivity mismatch, a policy designed to block requests containing specific header values fails open: the rule is evaluated as a non-match, and traffic that should have been rejected is served.

Furthermore, gRFC A41 requires rejecting configuration schemas specifying header matchers starting with grpc-. Because this check is executed case-sensitively in grpc-go, attackers can bypass the validation by specifying titles like Grpc-Status.

Patches

The problem is fixed in master and in the 1.83.1 release.

Impact

An unauthenticated remote attacker can initiate a gRPC stream and purposefully fragment their payload into millions of tiny (e.g., 1-byte) HTTP/2 DATA frames. Even if the total payload volume falls within the configured connection and stream flow-control windows, each independent fragment incurs memory overhead due to internal tracking structures and queue allocation.

Repeated fragmentation massively inflates the heap space consumed by the stream. An attacker multiplexing multiple concurrent streams can exhaust the memory bounds of the runtime, forcing a runtime panic or OutOfMemory condition and leading to a remote Denial of Service (DoS).

Patches

The change to fix this issue is merged in master and a patch release, 1.83.1, has been published that contains this fix.

Workarounds

This vulnerability is mitigated by implementing receive buffer compaction. Consecutive small data buffers are automatically coalesced into larger buffers from a shared pool once the overhead is perceived to be excessive relative to actual payload data, drastically minimizing per-frame memory overheads.

This behavior is enabled by default. A temporary escape hatch is provided via the environment variable GRPC_GO_EXPERIMENTAL_ENABLE_RECEIVE_BUFFER_COMPACTION=false to disable the feature if unforeseen issues arise, but it will be removed in a future release.

Vulnerabilities in the xDS RBAC authorization engine and the HTTP/2 transport server implementation in google.golang.org/grpc

Authorization bypass in gRPC-Go via missing leading slash in :path in google.golang.org/grpc

A vulnerability exists in gRPC-Go servers configured with xds.NewGRPCServer() where a crafted request missing both :authority and Host headers can cause a server panic, resulting in a Denial of Service (DoS).

Servers built with xds.NewGRPCServer install an xDS routing interceptor on every RPC. This interceptor looks up the request’s :authority header to pick a virtual host. The HTTP/2 server transport previously accepted requests that had neither :authority nor Host. When this happened, the xDS routing interceptor attempted to access the first element of an empty slice of authorities, leading to an index out of bounds panic. Since the per-RPC goroutine does not recover from panics, the entire server process would terminate.

This panic occurs in the interceptor pipeline, meaning the transport credentials handshake (TLS, mTLS, or ALTS) and HTTP/2 connection establishment must complete successfully before the crafted request can reach this logic.

• Insecure/Standard TLS: If the server permits insecure (plaintext) connections or standard credentials (where client certs are not checked), any unauthenticated remote attacker can trigger the crash.
• mTLS / ALTS: If strict transport-level authentication is enforced at the network edge or transport layer (e.g., requiring a valid client certificate), the attacker must possess valid transport credentials to initiate the stream and trigger the panic.

Impact

An attacker can cause a complete outage of the gRPC server by sending a request missing both :authority and Host headers, provided they can successfully establish a transport connection.

Patches

The issue has been addressed in master (and backported to 1.83.2 and 1.82.2). The fix updates the HTTP/2 transport layer to reject requests missing both :authority and Host headers early, maintaining consistency with and other gRPC language implementations.

Summary

A vulnerability in the xDS RBAC HTTP filter implementation in grpc-go allows remote attackers to bypass authorization policies (specifically DENY rules) by using mixed-case or canonical-case header matchers (e.g., X-Role instead of x-role). Additionally, the safety guards introduced by gRFC A41 to block grpc- prefixed headers can be evaded via variations in casing (e.g., Grpc-Status).

Impact

When an operator defines an RBAC policy referencing headers containing uppercase letters (e.g. X-Role), grpc-go fails to match incoming metadata keys because they are unconditionally lowercased. Because of this case-sensitivity mismatch, a policy designed to block requests containing specific header values fails open: the rule is evaluated as a non-match, and traffic that should have been rejected is served.

Furthermore, gRFC A41 requires rejecting configuration schemas specifying header matchers starting with grpc-. Because this check is executed case-sensitively in grpc-go, attackers can bypass the validation by specifying titles like Grpc-Status.

Patches

The problem is fixed in master and in the 1.83.1 release.

Impact

An unauthenticated remote attacker can initiate a gRPC stream and purposefully fragment their payload into millions of tiny (e.g., 1-byte) HTTP/2 DATA frames. Even if the total payload volume falls within the configured connection and stream flow-control windows, each independent fragment incurs memory overhead due to internal tracking structures and queue allocation.

Repeated fragmentation massively inflates the heap space consumed by the stream. An attacker multiplexing multiple concurrent streams can exhaust the memory bounds of the runtime, forcing a runtime panic or OutOfMemory condition and leading to a remote Denial of Service (DoS).

Patches

The change to fix this issue is merged in master and a patch release, 1.83.1, has been published that contains this fix.

Workarounds

This vulnerability is mitigated by implementing receive buffer compaction. Consecutive small data buffers are automatically coalesced into larger buffers from a shared pool once the overhead is perceived to be excessive relative to actual payload data, drastically minimizing per-frame memory overheads.

This behavior is enabled by default. A temporary escape hatch is provided via the environment variable GRPC_GO_EXPERIMENTAL_ENABLE_RECEIVE_BUFFER_COMPACTION=false to disable the feature if unforeseen issues arise, but it will be removed in a future release.

Vulnerabilities in the xDS RBAC authorization engine and the HTTP/2 transport server implementation in google.golang.org/grpc

Authorization bypass in gRPC-Go via missing leading slash in :path in google.golang.org/grpc

A vulnerability exists in gRPC-Go servers configured with xds.NewGRPCServer() where a crafted request missing both :authority and Host headers can cause a server panic, resulting in a Denial of Service (DoS).

Servers built with xds.NewGRPCServer install an xDS routing interceptor on every RPC. This interceptor looks up the request’s :authority header to pick a virtual host. The HTTP/2 server transport previously accepted requests that had neither :authority nor Host. When this happened, the xDS routing interceptor attempted to access the first element of an empty slice of authorities, leading to an index out of bounds panic. Since the per-RPC goroutine does not recover from panics, the entire server process would terminate.

This panic occurs in the interceptor pipeline, meaning the transport credentials handshake (TLS, mTLS, or ALTS) and HTTP/2 connection establishment must complete successfully before the crafted request can reach this logic.

• Insecure/Standard TLS: If the server permits insecure (plaintext) connections or standard credentials (where client certs are not checked), any unauthenticated remote attacker can trigger the crash.
• mTLS / ALTS: If strict transport-level authentication is enforced at the network edge or transport layer (e.g., requiring a valid client certificate), the attacker must possess valid transport credentials to initiate the stream and trigger the panic.

Impact

An attacker can cause a complete outage of the gRPC server by sending a request missing both :authority and Host headers, provided they can successfully establish a transport connection.

Patches

The issue has been addressed in master (and backported to 1.83.2 and 1.82.2). The fix updates the HTTP/2 transport layer to reject requests missing both :authority and Host headers early, maintaining consistency with and other gRPC language implementations.

Summary

A vulnerability in the xDS RBAC HTTP filter implementation in grpc-go allows remote attackers to bypass authorization policies (specifically DENY rules) by using mixed-case or canonical-case header matchers (e.g., X-Role instead of x-role). Additionally, the safety guards introduced by gRFC A41 to block grpc- prefixed headers can be evaded via variations in casing (e.g., Grpc-Status).

Impact

When an operator defines an RBAC policy referencing headers containing uppercase letters (e.g. X-Role), grpc-go fails to match incoming metadata keys because they are unconditionally lowercased. Because of this case-sensitivity mismatch, a policy designed to block requests containing specific header values fails open: the rule is evaluated as a non-match, and traffic that should have been rejected is served.

Furthermore, gRFC A41 requires rejecting configuration schemas specifying header matchers starting with grpc-. Because this check is executed case-sensitively in grpc-go, attackers can bypass the validation by specifying titles like Grpc-Status.

Patches

The problem is fixed in master and in the 1.83.1 release.

Impact

An unauthenticated remote attacker can initiate a gRPC stream and purposefully fragment their payload into millions of tiny (e.g., 1-byte) HTTP/2 DATA frames. Even if the total payload volume falls within the configured connection and stream flow-control windows, each independent fragment incurs memory overhead due to internal tracking structures and queue allocation.

Repeated fragmentation massively inflates the heap space consumed by the stream. An attacker multiplexing multiple concurrent streams can exhaust the memory bounds of the runtime, forcing a runtime panic or OutOfMemory condition and leading to a remote Denial of Service (DoS).

Patches

The change to fix this issue is merged in master and a patch release, 1.83.1, has been published that contains this fix.

Workarounds

This vulnerability is mitigated by implementing receive buffer compaction. Consecutive small data buffers are automatically coalesced into larger buffers from a shared pool once the overhead is perceived to be excessive relative to actual payload data, drastically minimizing per-frame memory overheads.

This behavior is enabled by default. A temporary escape hatch is provided via the environment variable GRPC_GO_EXPERIMENTAL_ENABLE_RECEIVE_BUFFER_COMPACTION=false to disable the feature if unforeseen issues arise, but it will be removed in a future release.

Vulnerabilities in the xDS RBAC authorization engine and the HTTP/2 transport server implementation in google.golang.org/grpc

Authorization bypass in gRPC-Go via missing leading slash in :path in google.golang.org/grpc

A vulnerability exists in gRPC-Go servers configured with xds.NewGRPCServer() where a crafted request missing both :authority and Host headers can cause a server panic, resulting in a Denial of Service (DoS).

Servers built with xds.NewGRPCServer install an xDS routing interceptor on every RPC. This interceptor looks up the request’s :authority header to pick a virtual host. The HTTP/2 server transport previously accepted requests that had neither :authority nor Host. When this happened, the xDS routing interceptor attempted to access the first element of an empty slice of authorities, leading to an index out of bounds panic. Since the per-RPC goroutine does not recover from panics, the entire server process would terminate.

This panic occurs in the interceptor pipeline, meaning the transport credentials handshake (TLS, mTLS, or ALTS) and HTTP/2 connection establishment must complete successfully before the crafted request can reach this logic.

• Insecure/Standard TLS: If the server permits insecure (plaintext) connections or standard credentials (where client certs are not checked), any unauthenticated remote attacker can trigger the crash.
• mTLS / ALTS: If strict transport-level authentication is enforced at the network edge or transport layer (e.g., requiring a valid client certificate), the attacker must possess valid transport credentials to initiate the stream and trigger the panic.

Impact

An attacker can cause a complete outage of the gRPC server by sending a request missing both :authority and Host headers, provided they can successfully establish a transport connection.

Patches

The issue has been addressed in master (and backported to 1.83.2 and 1.82.2). The fix updates the HTTP/2 transport layer to reject requests missing both :authority and Host headers early, maintaining consistency with and other gRPC language implementations.

Summary

A vulnerability in the xDS RBAC HTTP filter implementation in grpc-go allows remote attackers to bypass authorization policies (specifically DENY rules) by using mixed-case or canonical-case header matchers (e.g., X-Role instead of x-role). Additionally, the safety guards introduced by gRFC A41 to block grpc- prefixed headers can be evaded via variations in casing (e.g., Grpc-Status).

Impact

When an operator defines an RBAC policy referencing headers containing uppercase letters (e.g. X-Role), grpc-go fails to match incoming metadata keys because they are unconditionally lowercased. Because of this case-sensitivity mismatch, a policy designed to block requests containing specific header values fails open: the rule is evaluated as a non-match, and traffic that should have been rejected is served.

Furthermore, gRFC A41 requires rejecting configuration schemas specifying header matchers starting with grpc-. Because this check is executed case-sensitively in grpc-go, attackers can bypass the validation by specifying titles like Grpc-Status.

Patches

The problem is fixed in master and in the 1.83.1 release.

Impact

An unauthenticated remote attacker can initiate a gRPC stream and purposefully fragment their payload into millions of tiny (e.g., 1-byte) HTTP/2 DATA frames. Even if the total payload volume falls within the configured connection and stream flow-control windows, each independent fragment incurs memory overhead due to internal tracking structures and queue allocation.

Repeated fragmentation massively inflates the heap space consumed by the stream. An attacker multiplexing multiple concurrent streams can exhaust the memory bounds of the runtime, forcing a runtime panic or OutOfMemory condition and leading to a remote Denial of Service (DoS).

Patches

The change to fix this issue is merged in master and a patch release, 1.83.1, has been published that contains this fix.

Workarounds

This vulnerability is mitigated by implementing receive buffer compaction. Consecutive small data buffers are automatically coalesced into larger buffers from a shared pool once the overhead is perceived to be excessive relative to actual payload data, drastically minimizing per-frame memory overheads.

This behavior is enabled by default. A temporary escape hatch is provided via the environment variable GRPC_GO_EXPERIMENTAL_ENABLE_RECEIVE_BUFFER_COMPACTION=false to disable the feature if unforeseen issues arise, but it will be removed in a future release.

Vulnerabilities in the xDS RBAC authorization engine and the HTTP/2 transport server implementation in google.golang.org/grpc

Authorization bypass in gRPC-Go via missing leading slash in :path in google.golang.org/grpc

A vulnerability exists in gRPC-Go servers configured with xds.NewGRPCServer() where a crafted request missing both :authority and Host headers can cause a server panic, resulting in a Denial of Service (DoS).

Servers built with xds.NewGRPCServer install an xDS routing interceptor on every RPC. This interceptor looks up the request’s :authority header to pick a virtual host. The HTTP/2 server transport previously accepted requests that had neither :authority nor Host. When this happened, the xDS routing interceptor attempted to access the first element of an empty slice of authorities, leading to an index out of bounds panic. Since the per-RPC goroutine does not recover from panics, the entire server process would terminate.

This panic occurs in the interceptor pipeline, meaning the transport credentials handshake (TLS, mTLS, or ALTS) and HTTP/2 connection establishment must complete successfully before the crafted request can reach this logic.

• Insecure/Standard TLS: If the server permits insecure (plaintext) connections or standard credentials (where client certs are not checked), any unauthenticated remote attacker can trigger the crash.
• mTLS / ALTS: If strict transport-level authentication is enforced at the network edge or transport layer (e.g., requiring a valid client certificate), the attacker must possess valid transport credentials to initiate the stream and trigger the panic.

Impact

An attacker can cause a complete outage of the gRPC server by sending a request missing both :authority and Host headers, provided they can successfully establish a transport connection.

Patches

The issue has been addressed in master (and backported to 1.83.2 and 1.82.2). The fix updates the HTTP/2 transport layer to reject requests missing both :authority and Host headers early, maintaining consistency with and other gRPC language implementations.

Summary

A vulnerability in the xDS RBAC HTTP filter implementation in grpc-go allows remote attackers to bypass authorization policies (specifically DENY rules) by using mixed-case or canonical-case header matchers (e.g., X-Role instead of x-role). Additionally, the safety guards introduced by gRFC A41 to block grpc- prefixed headers can be evaded via variations in casing (e.g., Grpc-Status).

Impact

When an operator defines an RBAC policy referencing headers containing uppercase letters (e.g. X-Role), grpc-go fails to match incoming metadata keys because they are unconditionally lowercased. Because of this case-sensitivity mismatch, a policy designed to block requests containing specific header values fails open: the rule is evaluated as a non-match, and traffic that should have been rejected is served.

Furthermore, gRFC A41 requires rejecting configuration schemas specifying header matchers starting with grpc-. Because this check is executed case-sensitively in grpc-go, attackers can bypass the validation by specifying titles like Grpc-Status.

Patches

The problem is fixed in master and in the 1.83.1 release.

Impact

An unauthenticated remote attacker can initiate a gRPC stream and purposefully fragment their payload into millions of tiny (e.g., 1-byte) HTTP/2 DATA frames. Even if the total payload volume falls within the configured connection and stream flow-control windows, each independent fragment incurs memory overhead due to internal tracking structures and queue allocation.

Repeated fragmentation massively inflates the heap space consumed by the stream. An attacker multiplexing multiple concurrent streams can exhaust the memory bounds of the runtime, forcing a runtime panic or OutOfMemory condition and leading to a remote Denial of Service (DoS).

Patches

The change to fix this issue is merged in master and a patch release, 1.83.1, has been published that contains this fix.

Workarounds

This vulnerability is mitigated by implementing receive buffer compaction. Consecutive small data buffers are automatically coalesced into larger buffers from a shared pool once the overhead is perceived to be excessive relative to actual payload data, drastically minimizing per-frame memory overheads.

This behavior is enabled by default. A temporary escape hatch is provided via the environment variable GRPC_GO_EXPERIMENTAL_ENABLE_RECEIVE_BUFFER_COMPACTION=false to disable the feature if unforeseen issues arise, but it will be removed in a future release.

Vulnerabilities in the xDS RBAC authorization engine and the HTTP/2 transport server implementation in google.golang.org/grpc

Authorization bypass in gRPC-Go via missing leading slash in :path in google.golang.org/grpc

A vulnerability exists in gRPC-Go servers configured with xds.NewGRPCServer() where a crafted request missing both :authority and Host headers can cause a server panic, resulting in a Denial of Service (DoS).

Servers built with xds.NewGRPCServer install an xDS routing interceptor on every RPC. This interceptor looks up the request’s :authority header to pick a virtual host. The HTTP/2 server transport previously accepted requests that had neither :authority nor Host. When this happened, the xDS routing interceptor attempted to access the first element of an empty slice of authorities, leading to an index out of bounds panic. Since the per-RPC goroutine does not recover from panics, the entire server process would terminate.

This panic occurs in the interceptor pipeline, meaning the transport credentials handshake (TLS, mTLS, or ALTS) and HTTP/2 connection establishment must complete successfully before the crafted request can reach this logic.

• Insecure/Standard TLS: If the server permits insecure (plaintext) connections or standard credentials (where client certs are not checked), any unauthenticated remote attacker can trigger the crash.
• mTLS / ALTS: If strict transport-level authentication is enforced at the network edge or transport layer (e.g., requiring a valid client certificate), the attacker must possess valid transport credentials to initiate the stream and trigger the panic.

Impact

An attacker can cause a complete outage of the gRPC server by sending a request missing both :authority and Host headers, provided they can successfully establish a transport connection.

Patches

The issue has been addressed in master (and backported to 1.83.2 and 1.82.2). The fix updates the HTTP/2 transport layer to reject requests missing both :authority and Host headers early, maintaining consistency with and other gRPC language implementations.

Summary

A vulnerability in the xDS RBAC HTTP filter implementation in grpc-go allows remote attackers to bypass authorization policies (specifically DENY rules) by using mixed-case or canonical-case header matchers (e.g., X-Role instead of x-role). Additionally, the safety guards introduced by gRFC A41 to block grpc- prefixed headers can be evaded via variations in casing (e.g., Grpc-Status).

Impact

When an operator defines an RBAC policy referencing headers containing uppercase letters (e.g. X-Role), grpc-go fails to match incoming metadata keys because they are unconditionally lowercased. Because of this case-sensitivity mismatch, a policy designed to block requests containing specific header values fails open: the rule is evaluated as a non-match, and traffic that should have been rejected is served.

Furthermore, gRFC A41 requires rejecting configuration schemas specifying header matchers starting with grpc-. Because this check is executed case-sensitively in grpc-go, attackers can bypass the validation by specifying titles like Grpc-Status.

Patches

The problem is fixed in master and in the 1.83.1 release.

Impact

An unauthenticated remote attacker can initiate a gRPC stream and purposefully fragment their payload into millions of tiny (e.g., 1-byte) HTTP/2 DATA frames. Even if the total payload volume falls within the configured connection and stream flow-control windows, each independent fragment incurs memory overhead due to internal tracking structures and queue allocation.

Repeated fragmentation massively inflates the heap space consumed by the stream. An attacker multiplexing multiple concurrent streams can exhaust the memory bounds of the runtime, forcing a runtime panic or OutOfMemory condition and leading to a remote Denial of Service (DoS).

Patches

The change to fix this issue is merged in master and a patch release, 1.83.1, has been published that contains this fix.

Workarounds

This vulnerability is mitigated by implementing receive buffer compaction. Consecutive small data buffers are automatically coalesced into larger buffers from a shared pool once the overhead is perceived to be excessive relative to actual payload data, drastically minimizing per-frame memory overheads.

This behavior is enabled by default. A temporary escape hatch is provided via the environment variable GRPC_GO_EXPERIMENTAL_ENABLE_RECEIVE_BUFFER_COMPACTION=false to disable the feature if unforeseen issues arise, but it will be removed in a future release.

Vulnerabilities in the xDS RBAC authorization engine and the HTTP/2 transport server implementation in google.golang.org/grpc

Authorization bypass in gRPC-Go via missing leading slash in :path in google.golang.org/grpc

A vulnerability exists in gRPC-Go servers configured with xds.NewGRPCServer() where a crafted request missing both :authority and Host headers can cause a server panic, resulting in a Denial of Service (DoS).

Servers built with xds.NewGRPCServer install an xDS routing interceptor on every RPC. This interceptor looks up the request’s :authority header to pick a virtual host. The HTTP/2 server transport previously accepted requests that had neither :authority nor Host. When this happened, the xDS routing interceptor attempted to access the first element of an empty slice of authorities, leading to an index out of bounds panic. Since the per-RPC goroutine does not recover from panics, the entire server process would terminate.

This panic occurs in the interceptor pipeline, meaning the transport credentials handshake (TLS, mTLS, or ALTS) and HTTP/2 connection establishment must complete successfully before the crafted request can reach this logic.

• Insecure/Standard TLS: If the server permits insecure (plaintext) connections or standard credentials (where client certs are not checked), any unauthenticated remote attacker can trigger the crash.
• mTLS / ALTS: If strict transport-level authentication is enforced at the network edge or transport layer (e.g., requiring a valid client certificate), the attacker must possess valid transport credentials to initiate the stream and trigger the panic.

Impact

An attacker can cause a complete outage of the gRPC server by sending a request missing both :authority and Host headers, provided they can successfully establish a transport connection.

Patches

The issue has been addressed in master (and backported to 1.83.2 and 1.82.2). The fix updates the HTTP/2 transport layer to reject requests missing both :authority and Host headers early, maintaining consistency with and other gRPC language implementations.

Summary

A vulnerability in the xDS RBAC HTTP filter implementation in grpc-go allows remote attackers to bypass authorization policies (specifically DENY rules) by using mixed-case or canonical-case header matchers (e.g., X-Role instead of x-role). Additionally, the safety guards introduced by gRFC A41 to block grpc- prefixed headers can be evaded via variations in casing (e.g., Grpc-Status).

Impact

When an operator defines an RBAC policy referencing headers containing uppercase letters (e.g. X-Role), grpc-go fails to match incoming metadata keys because they are unconditionally lowercased. Because of this case-sensitivity mismatch, a policy designed to block requests containing specific header values fails open: the rule is evaluated as a non-match, and traffic that should have been rejected is served.

Furthermore, gRFC A41 requires rejecting configuration schemas specifying header matchers starting with grpc-. Because this check is executed case-sensitively in grpc-go, attackers can bypass the validation by specifying titles like Grpc-Status.

Patches

The problem is fixed in master and in the 1.83.1 release.

Impact

An unauthenticated remote attacker can initiate a gRPC stream and purposefully fragment their payload into millions of tiny (e.g., 1-byte) HTTP/2 DATA frames. Even if the total payload volume falls within the configured connection and stream flow-control windows, each independent fragment incurs memory overhead due to internal tracking structures and queue allocation.

Repeated fragmentation massively inflates the heap space consumed by the stream. An attacker multiplexing multiple concurrent streams can exhaust the memory bounds of the runtime, forcing a runtime panic or OutOfMemory condition and leading to a remote Denial of Service (DoS).

Patches

The change to fix this issue is merged in master and a patch release, 1.83.1, has been published that contains this fix.

Workarounds

This vulnerability is mitigated by implementing receive buffer compaction. Consecutive small data buffers are automatically coalesced into larger buffers from a shared pool once the overhead is perceived to be excessive relative to actual payload data, drastically minimizing per-frame memory overheads.

This behavior is enabled by default. A temporary escape hatch is provided via the environment variable GRPC_GO_EXPERIMENTAL_ENABLE_RECEIVE_BUFFER_COMPACTION=false to disable the feature if unforeseen issues arise, but it will be removed in a future release.

Vulnerabilities in the xDS RBAC authorization engine and the HTTP/2 transport server implementation in google.golang.org/grpc

Authorization bypass in gRPC-Go via missing leading slash in :path in google.golang.org/grpc