grpc grpc-go up to 1.79.2 improper authorization

Summaryinfo

A vulnerability was found in grpc grpc-go up to 1.79.2. It has been rated as critical. The affected element is an unknown function. Performing a manipulation results in improper authorization. This vulnerability is cataloged as CVE-2026-33186. It is possible to initiate the attack remotely. There is no exploit available. Upgrading the affected component is advised.

Detailsinfo

A vulnerability was found in grpc grpc-go up to 1.79.2. It has been classified as critical. This affects an unknown function. The manipulation with an unknown input leads to a improper authorization vulnerability. CWE is classifying the issue as CWE-285. The product does not perform or incorrectly performs an authorization check when an actor attempts to access a resource or perform an action. This is going to have an impact on confidentiality, integrity, and availability. The summary by CVE is:

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 with a non-canonical path string. While upgrading is the most secure and recommended path, users can mitigate the vulnerability using one of the following methods: Use a validating interceptor (recommended mitigation); infrastructure-level normalization; and/or policy hardening.

The advisory is shared at github.com. This vulnerability is uniquely identified as CVE-2026-33186 since 03/17/2026. The exploitability is told to be easy. It is possible to initiate the attack remotely. No form of authentication is needed for exploitation. Neither technical details nor an exploit are publicly available. MITRE ATT&CK project uses the attack technique T1548.002 for this issue.

The vulnerability scanner Nessus provides a plugin with the ID 303458 (Linux Distros Unpatched Vulnerability : CVE-2026-33186), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 1.79.3 eliminates this vulnerability.

The vulnerability is also documented in the databases at Tenable (303458), EUVD (EUVD-2026-13830) and CERT Bund (WID-SEC-2026-1136). If you want to get the best quality for vulnerability data then you always have to consider VulDB.

Affected

• Red Hat Enterprise Linux
• SUSE Linux
• SUSE openSUSE
• RESF Rocky Linux
• Red Hat OpenShift
• IBM MQ
• IBM DB2
• IBM App Connect Enterprise
• IBM Storage Scale
• SolarWinds Platform
• Oracle Linux

Productinfo

Vendor

• grpc

Name

• grpc-go

Version

• 1.79.0
• 1.79.1
• 1.79.2

Website

• Product: https://github.com/grpc/grpc-go/

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If you want to get the best quality for vulnerability data then you always have to consider VulDB.

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