Vulnerability Description
gRPC-Go is the Go language implementation of gRPC. Prior to 1.83.1, the xDS RBAC HTTP filter in internal/xds/httpfilter/rbac/rbac.go does not lowercase header matcher names in normalizeHeaderMatcher even though incoming metadata keys are lowercase. A DENY policy using a mixed-case name such as X-Role or User-Agent therefore does not match and fails open, allowing requests that should be rejected. The same case mismatch permits :Scheme or Grpc-Status to evade gRFC A41 validation and prevents Host from being rewritten to :authority. This issue is fixed in version 1.83.1.
Related Weaknesses (CWE)
References
- https://github.com/grpc/grpc-go/commit/db9482836c298f234c896cf82ab68cafc78237f8
- https://github.com/grpc/grpc-go/commit/ebba6f3f1b206e2b4dc4d1d5a96d18430302c2fe
- https://github.com/grpc/grpc-go/pull/9332
- https://github.com/grpc/grpc-go/pull/9335
- https://github.com/grpc/grpc-go/releases/tag/v1.83.1
- https://github.com/grpc/grpc-go/security/advisories/GHSA-qc2q-p7wx-3px3
FAQ
What is CVE-2026-84303?
CVE-2026-84303 is a documented vulnerability. gRPC-Go is the Go language implementation of gRPC. Prior to 1.83.1, the xDS RBAC HTTP filter in internal/xds/httpfilter/rbac/rbac.go does not lowercase header matcher names in normalizeHeaderMatcher e...
How severe is CVE-2026-84303?
CVSS scoring is not yet available for CVE-2026-84303. Check NVD for updates.
Is there a patch for CVE-2026-84303?
Check the references section above for vendor advisories and patch information. Review vendor security bulletins for remediation guidance.