Affected: grpc-go, Red Hat Cryostat 4 on RHEL 9, Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 10.0 Extended Update Support, Red Hat Enterprise Linux 7 Extended Lifecycle Support, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 9, Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions, Red Hat Enterprise Linux 9.4 Extended Update Support, Red Hat Enterprise Linux 9.4 Update Services for SAP Solutions and 158 more

gRPC-Go is the Go language implementation of gRPC. Versions prior to 1.79.3 have an authorization bypass resulting from improper input validation of the HTTP/2 `:path` pseudo-header. The gRPC-Go server was too lenient in its routing logic, accepting requests where the `:path` omitted the mandatory leading slash (e.g., `Service/Method` instead of `/Service/Method`). While the server successfully routed these requests to the correct handler, authorization interceptors (including the official `grpc/authz` package) evaluated the raw, non-canonical path string. Consequently, "deny" rules defined using canonical paths (starting with `/`) failed to match the incoming request, allowing it to bypass the policy if a fallback "allow" rule was present. This affects gRPC-Go servers that use path-based authorization interceptors, such as the official RBAC implementation in `google.golang.org/grpc/authz` or custom interceptors relying on `info.FullMethod` or `grpc.Method(ctx)`; AND that have a security policy contains specific "deny" rules for canonical paths but allows other requests by default (a fallback "allow" rule). The vulnerability is exploitable by an attacker who can send raw HTTP/2 frames with malformed `:path` headers directly to the gRPC server. The fix in version 1.79.3 ensures that any request with a `:path` that does not start with a leading slash is immediately rejected with a `codes.Unimplemented` error, preventing it from reaching authorization interceptors or handlers w…

Affected: Go: google.golang.org/grpc

Multiple security vulnerabilities have been identified and addressed in grpc-go affecting the xDS RBAC authorization engine (internal/xds/rbac) and the HTTP/2 transport server implementation (internal/transport). These vulnerabilities could result in:

- Authorization Bypass (Fail-Open) when translating xDS RBAC policies containing `Metadata` or `RequestedServerName` fields. - Denial of Service (High CPU Consumption) due to an HTTP/2 Rapid Reset mitigation bypass during client-initiated stream resets. - Denial of Service (Server Panic) when parsing crafted xDS RBAC policies containing `NOT` rules around unsupported fields.

### Impact _What kind of vulnerability is it? Who is impacted?_

#### xDS RBAC Authorization Bypass via `Metadata` & `RequestedServerName` matchers

- Affected Component: xDS RBAC - Impact: When building policy matchers for gRPC RBAC from xDS configurations, unsupported `permission` and `principal` rules (specifically `Metadata` and `RequestedServerName`) were silently ignored and treated as no-ops. - If an authorization policy relied purely on these matchers for access control, treating those rules as no-ops effectively removed the restrictions. - If these unsupported rules were nested inside logical `NOT` rules (`Permission_NotRule` / `Principal_NotId`) or multi-condition `OR/AND` rules, silently dropping them changed the boolean logic flow of the authorization engine.

As a result, policy evaluation decisions could fail open, allowing unauthorized…