{"id":"CVE-2026-84303","aliases":["GHSA-qc2q-p7wx-3px3"],"url":"https://o3.security/vulnerability/CVE-2026-84303","summary":"gRPC-Go: xDS RBAC HTTP Filter bypass via mixed-case Header Matching and gRFC A41 validation evasion","details":"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.","published":"2026-09-01T18:14:37.870Z","modified":"2026-09-08T12:38:48.650399129Z","cvss":null,"epss":null,"cisaKev":null,"exploitsKnown":null,"affectedPackages":[{"ecosystem":"Go","name":"google.golang.org/grpc","fixedVersion":"1.83.1"}],"fix":{"url":"https://github.com/grpc/grpc-go/commit/db9482836c298f234c896cf82ab68cafc78237f8","label":"grpc/grpc-go@db94828"},"references":[{"type":"WEB","url":"https://github.com/grpc/grpc-go/releases/tag/v1.83.1"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/84xxx/CVE-2026-84303.json"},{"type":"ADVISORY","url":"https://github.com/grpc/grpc-go/security/advisories/GHSA-qc2q-p7wx-3px3"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-84303"},{"type":"FIX","url":"https://github.com/grpc/grpc-go/commit/db9482836c298f234c896cf82ab68cafc78237f8"},{"type":"FIX","url":"https://github.com/grpc/grpc-go/commit/ebba6f3f1b206e2b4dc4d1d5a96d18430302c2fe"},{"type":"FIX","url":"https://github.com/grpc/grpc-go/pull/9332"},{"type":"FIX","url":"https://github.com/grpc/grpc-go/pull/9335"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-09-08T12:38:48.650399129Z"}}