go.mod: update module google.golang.org/grpc to v1.79.3 [SECURITY]

[renovate]

This PR contains the following updates:

Package	Change	Age	Confidence
google.golang.org/grpc	v1.78.0 → v1.79.3

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gRPC-Go has an authorization bypass via missing leading slash in :path

CVE-2026-33186 / GHSA-p77j-4mvh-x3m3 / GO-2026-4762

More information

Details

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:

1. They 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).
2. 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.

Severity

• CVSS Score: 9.1 / 10 (Critical)
• Vector String: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

References

• https://github.com/grpc/grpc-go/security/advisories/GHSA-p77j-4mvh-x3m3
• https://nvd.nist.gov/vuln/detail/CVE-2026-33186
• https://github.com/grpc/grpc-go

This data is provided by OSV and the GitHub Advisory Database (CC-BY 4.0).

---

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

CVE-2026-33186 / GHSA-p77j-4mvh-x3m3 / GO-2026-4762

More information

Details

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

Severity

Unknown

References

• https://github.com/grpc/grpc-go/security/advisories/GHSA-p77j-4mvh-x3m3

This data is provided by OSV and the Go Vulnerability Database (CC-BY 4.0).

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Release Notes

grpc/grpc-go (google.golang.org/grpc)

v1.79.3: Release 1.79.3

Compare Source

Security

• server: fix an authorization bypass where malformed :path headers (missing the leading slash) could bypass path-based restricted "deny" rules in interceptors like grpc/authz. Any request with a non-canonical path is now immediately rejected with an Unimplemented error. (#​8981)

v1.79.2: Release 1.79.2

Compare Source

Bug Fixes

• stats: Prevent redundant error logging in health/ORCA producers by skipping stats/tracing processing when no stats handler is configured. (#​8874)

v1.79.1: Release 1.79.1

Compare Source

Bug Fixes

• grpc: Remove the -dev suffix from the User-Agent header. (#​8902)

v1.79.0: Release 1.79.0

Compare Source

API Changes

• mem: Add experimental API SetDefaultBufferPool to change the default buffer pool. (#​8806)
  • Special Thanks: @​vanja-p
• experimental/stats: Update MetricsRecorder to require embedding the new UnimplementedMetricsRecorder (a no-op struct) in all implementations for forward compatibility. (#​8780)

Behavior Changes

• balancer/weightedtarget: Remove handling of Addresses and only handle Endpoints in resolver updates. (#​8841)

New Features

• experimental/stats: Add support for asynchronous gauge metrics through the new AsyncMetricReporter and RegisterAsyncReporter APIs. (#​8780)
• pickfirst: Add support for weighted random shuffling of endpoints, as described in gRFC A113.
  • This is enabled by default, and can be turned off using the environment variable GRPC_EXPERIMENTAL_PF_WEIGHTED_SHUFFLING. (#​8864)
• xds: Implement :authority rewriting, as specified in gRFC A81. (#​8779)
• balancer/randomsubsetting: Implement the random_subsetting LB policy, as specified in gRFC A68. (#​8650)
  • Special Thanks: @​marek-szews
• server: Include status detail headers, if available, when terminating a stream during request header processing. (#​8754)
  • Special Thanks: @​joybestourous

Bug Fixes

• credentials/tls: Fix a bug where the port was not stripped from the authority override before validation. (#​8726)
  • Special Thanks: @​Atul1710
• xds/priority: Fix a bug causing delayed failover to lower-priority clusters when a higher-priority cluster is stuck in CONNECTING state. (#​8813)
• health: Fix a bug where health checks failed for clients using legacy compression options (WithDecompressor or RPCDecompressor). (#​8765)
  • Special Thanks: @​sanki92
• transport: Fix an issue where the HTTP/2 server could skip header size checks when terminating a stream early. (#​8769)
  • Special Thanks: @​joybestourous

Performance Improvements

• credentials/alts: Optimize read buffer alignment to reduce copies. (#​8791)
• mem: Optimize pooling and creation of buffer objects. (#​8784)
• transport: Reduce slice re-allocations by reserving slice capacity. (#​8797)

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