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.
References6
- github.com/grpc/grpc-go/commit/db9482836c298f234c896cf82ab68caf…
- github.com/grpc/grpc-go/commit/ebba6f3f1b206e2b4dc4d1d5a96d1843…
- github.com/grpc/grpc-go/pull/9332
- github.com/grpc/grpc-go/pull/9335
- github.com/grpc/grpc-go/releases/tag/v1.83.1
- github.com/grpc/grpc-go/security/advisories/GHSA-qc2q-p7wx-3px3
Metrics
- CVSS 4.0
-
6.3
MEDIUM
Score source: CNA
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X - EPSS — exploit probability
- 0% percentile: 24 · as of 8 November 2026
- CWE
- CWE-178CWE-863
Could this be exploited in your environment?
A patch closes the known hole. A penetration test shows what an attacker can still reach — with proof.