Vulnerability · Published Sep 1, 2026 · Assigned by GitHub_M
CVE-2026-84303gRPC-Go: xDS RBAC HTTP Filter bypass via mixed-case Header Matching and gRFC A41 validation evasion
Medium 6.3
In plain English
A medium-severity incorrect authorization in grpc-go from grpc. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 24% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official 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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | golang-google-grpc | no fix listed | DEBIAN-CVE-2026-84303 |
| Debian:13 | golang-google-grpc | no fix listed | DEBIAN-CVE-2026-84303 |
| Debian:14 | golang-google-grpc | no fix listed | DEBIAN-CVE-2026-84303 |
| Go | google.golang.org/grpc | 1.83.1 | GHSA-qc2q-p7wx-3px3 |
| Go | google.golang.org/grpc | 1.83.1 | GO-2026-6441 |
| Ubuntu:22.04:LTS | golang-google-grpc | no fix listed | UBUNTU-CVE-2026-84303 |
| Ubuntu:26.04:LTS | golang-google-grpc | no fix listed | UBUNTU-CVE-2026-84303 |
| Ubuntu:26.10 | golang-google-grpc | no fix listed | UBUNTU-CVE-2026-84303 |
| Ubuntu:22.04:LTS | google-guest-agent | no fix listed | UBUNTU-CVE-2026-84303 |
| Ubuntu:24.04:LTS | google-guest-agent | no fix listed | UBUNTU-CVE-2026-84303 |
| Ubuntu:26.04:LTS | google-guest-agent | no fix listed | UBUNTU-CVE-2026-84303 |
| Ubuntu:26.10 | google-guest-agent | no fix listed | UBUNTU-CVE-2026-84303 |
| Ubuntu:22.04:LTS | grpc | no fix listed | UBUNTU-CVE-2026-84303 |
| Ubuntu:24.04:LTS | grpc | no fix listed | UBUNTU-CVE-2026-84303 |
| Ubuntu:26.04:LTS | grpc | no fix listed | UBUNTU-CVE-2026-84303 |
| Ubuntu:26.10 | grpc | no fix listed | UBUNTU-CVE-2026-84303 |
Affected products (as reported)
Weakness: CWE-178, CWE-863 · Vector: 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
References
- https://github.com/grpc/grpc-go/security/advisories/GHSA-qc2q-p7wx-3px3 x_refsource_CONFIRM
- https://github.com/grpc/grpc-go/pull/9332 x_refsource_MISC
- https://github.com/grpc/grpc-go/pull/9335 x_refsource_MISC
- https://github.com/grpc/grpc-go/commit/db9482836c298f234c896cf82ab68cafc78237f8 x_refsource_MISC
- https://github.com/grpc/grpc-go/commit/ebba6f3f1b206e2b4dc4d1d5a96d18430302c2fe x_refsource_MISC
- https://github.com/grpc/grpc-go/releases/tag/v1.83.1 x_refsource_MISC