GHSA-qc2q-p7wx-3px3

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GHSA-qc2q-p7wx-3px3

Summary: gRPC-Go: xDS RBAC HTTP Filter bypass via mixed-case Header Matching and gRFC A41 validation evasion

Details: ### Summary A vulnerability in the xDS RBAC HTTP filter implementation in grpc-go allows remote attackers to bypass authorization policies (specifically DENY rules) by using mixed-case or canonical-case header matchers (e.g., X-Role instead of x-role). Additionally, the safety guards introduced by gRFC A41 to block grpc- prefixed headers can be evaded via variations in casing (e.g., Grpc-Status). ### Impact When an operator defines an RBAC policy referencing headers containing uppercase letters (e.g. X-Role), grpc-go fails to match incoming metadata keys because they are unconditionally lowercased. Because of this case-sensitivity mismatch, a policy designed to block requests containing specific header values fails open: the rule is evaluated as a non-match, and traffic that should have been rejected is served. Furthermore, gRFC A41 requires rejecting configuration schemas specifying header matchers starting with grpc-. Because this check is executed case-sensitively in grpc-go, attackers can bypass the validation by specifying titles like Grpc-Status. ### Patches The problem is fixed in `master` and in the 1.83.1 release.

References: https://github.com/grpc/grpc-go/security/advisories/GHSA-qc2q-p7wx-3px3, https://nvd.nist.gov/vuln/detail/CVE-2026-84303, https://github.com/grpc/grpc-go/pull/9332, https://github.com/grpc/grpc-go/pull/9335, https://github.com/grpc/grpc-go/commit/db9482836c298f234c896cf82ab68cafc78237f8, https://github.com/grpc/grpc-go/commit/ebba6f3f1b206e2b4dc4d1d5a96d18430302c2fe, https://github.com/grpc/grpc-go, https://github.com/grpc/grpc-go/releases/tag/v1.83.1