CVE-2026-84303

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.

• CWE-178
• CWE-863

• 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

Published

Sep 1, 2026

Last Modified

Sep 9, 2026

Status

Deferred

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