Machine-written summary
Summary written by Claude Haiku from the source advisory. Not reviewed by a person.
The gRPC-Go module google.golang.org/grpc before 1.83.1 is affected. In the xDS RBAC HTTP filter, header matchers that use uppercase letters, such as X-Role, never match incoming metadata, so DENY rules fail open and requests that should be rejected are served. A remote attacker can exploit this to bypass authorization policies without special access. The gRFC A41 check that blocks grpc- prefixed header matchers can also be evaded by changing letter case, such as Grpc-Status. Upgrade to google.golang.org/grpc 1.83.1.
Not analysed yet
We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.
Severity and exploitation
| Score | Rating | CVSS | Vector | Source |
|---|---|---|---|---|
| 6.3 | Medium | 4.0 | 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 | CNA (GitHub_M) |
- CISA KEV Not listed.
- EPSS 0.0031, the 24th percentile, on 5 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.
Timeline
- 31 Oct 2026, 14:13 UTC First seen by agentprime
- 31 Oct 2026, 14:13 UTC Confirmed by OSV
Sources
- GitHub Advisory Database: GHSA-qc2q-p7wx-3px3
- OSV: GHSA-qc2q-p7wx-3px3
- github.com/grpc/grpc-go/security/advisories/GHSA-qc2q-p7wx-3px3
- nvd.nist.gov/vuln/detail/CVE-2026-84303
- github.com/grpc/grpc-go/pull/9332
- github.com/grpc/grpc-go/pull/9335
- github.com/grpc/grpc-go/commit/db9482836c298f234c896cf82ab68cafc78237f8
- github.com/grpc/grpc-go/commit/ebba6f3f1b206e2b4dc4d1d5a96d18430302c2fe
- github.com/grpc/grpc-go
- github.com/grpc/grpc-go/releases/tag/v1.83.1