GHSA-p77j-4mvh-x3m3
CRITICALGHSA-p77j-4mvh-x3m3 is a critical-severity (CVSS 9.1) CWE-285 vulnerability in google.golang.org/grpc. O3 Security confirms whether GHSA-p77j-4mvh-x3m3 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
gRPC-Go has an authorization bypass via missing leading slash in :path
Blast Radius
google.golang.org/grpcReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.
Description
Impact
What kind of vulnerability is it? Who is impacted?
It is 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.
Who is impacted? This affects gRPC-Go servers that meet both of the following criteria:
- They use path-based authorization interceptors, such as the official RBAC implementation in
google.golang.org/grpc/authzor custom interceptors relying oninfo.FullMethodorgrpc.Method(ctx). - Their 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.
Patches
Has the problem been patched? What versions should users upgrade to?
Yes, the issue has been patched. The fix 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.
Users should upgrade to the following versions (or newer):
- v1.79.3
- The latest master branch.
It is recommended that all users employing path-based authorization (especially grpc/authz) upgrade as soon as the patch is available in a tagged release.
Workarounds
Is there a way for users to fix or remediate the vulnerability without upgrading?
While upgrading is the most secure and recommended path, users can mitigate the vulnerability using one of the following methods:
1. Use a Validating Interceptor (Recommended Mitigation)
Add an "outermost" interceptor to your server that validates the path before any other authorization logic runs:
func pathValidationInterceptor(ctx context.Context, req any, info *grpc.UnaryServerInfo, handler grpc.UnaryHandler) (any, error) {
if info.FullMethod == "" || info.FullMethod[0] != '/' {
return nil, status.Errorf(codes.Unimplemented, "malformed method name")
}
return handler(ctx, req)
}
// Ensure this is the FIRST interceptor in your chain
s := grpc.NewServer(
grpc.ChainUnaryInterceptor(pathValidationInterceptor, authzInterceptor),
)
2. Infrastructure-Level Normalization
If your gRPC server is behind a reverse proxy or load balancer (such as Envoy, NGINX, or an L7 Cloud Load Balancer), ensure it is configured to enforce strict HTTP/2 compliance for pseudo-headers and reject or normalize requests where the :path header does not start with a leading slash.
3. Policy Hardening
Switch to a "default deny" posture in your authorization policies (explicitly listing all allowed paths and denying everything else) to reduce the risk of bypasses via malformed inputs.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | google.golang.org/grpc | all versions | 1.79.3 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for google.golang.org/grpc. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update google.golang.org/grpc to 1.79.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-p77j-4mvh-x3m3 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-p77j-4mvh-x3m3 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-p77j-4mvh-x3m3. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-p77j-4mvh-x3m3 in your dependencies?
O3 detects GHSA-p77j-4mvh-x3m3 across Go dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.