gRPC-Go: xDS RBAC HTTP Filter bypass via mixed-case Header Matching and gRFC A41 validation evasion
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Attack requirements
- Present
- Impact type
- Security bypass
- Confidentiality · integrity · availability
- Low · Low · None
- Fix status
- Partial Red Hat: 1 without a fix
Attack profile from CVSS 4.0 · CNA. Fix status from CNA, GitHub and Red Hat. Impact type from CWE-863.
Summary
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.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- Yes
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| grpc | grpc-go | before 1.83.1 | 1.83.1 | Patch available | CNA |
| — | google.golang.org/grpc (Go) | before 1.83.1 | 1.83.1 | Patch available | GHSA-qc2q-p7wx-3px3 |
- grpc-go Vendorgrpc Affected before 1.83.1 Fixed in 1.83.1 Patch available CNA
- google.golang.org/grpc (Go) Vendor— Affected before 1.83.1 Fixed in 1.83.1 Patch available GHSA-qc2q-p7wx-3px3
Remediation
- Fix · CNA grpc-go (grpc) Fixed in 1.83.1
- Fix · GHSA-qc2q-p7wx-3px3 google.golang.org/grpc (Go) Fixed in 1.83.1 Advisory →
Vendor assessments
Red Hat
Red Hat rating: Moderate. Red Hat's page for this CVE →
| Product | Status | Plan or fix |
|---|---|---|
| Red Hat OpenShift AI (RHOAI) | Affected | No fix yet: Fix deferred |
Timeline
- 2026-10-02 Threatist record created from CVE-2026-84303
- 2026-10-03 Alias added: GHSA-qc2q-p7wx-3px3
- 2026-11-06 Affected versions changed · Red Hat
- 2026-11-06 CVSS score added · Red Hat
References
Other 7
- https://github.com/grpc/grpc-go/security/advisories/GHSA-qc2q-p7wx-3px3
- 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/releases/tag/v1.83.1
- https://github.com/grpc/grpc-go
More grpc vulnerabilities
- TI-2023-23979 The HTTP/2 protocol allows a denial of service (server resource consumption) because… KEVCVSS 3.1HIGH 7.5
- TI-2026-25614 gRPC-Go has an authorization bypass via missing leading slash in :path CVSS 3.1CRITICAL 9.1
- TI-2020-06285 Prototype pollution in grpc CVSS 3.1CRITICAL 9.8
- TI-2017-05916 Google gRPC before 2017-03-29 has an out-of-bounds write caused by a heap-based… CVSS 3.0CRITICAL 9.8
- TI-2017-05476 Google gRPC before 2017-02-22 has an out-of-bounds write caused by a heap-based buffer… CVSS 3.0CRITICAL 9.8
- TI-2017-06843 Google gRPC before 2017-04-05 has an out-of-bounds write caused by a heap-based buffer… CVSS 3.0CRITICAL 9.8
Sources
- CVE-2026-84303 · CVE Program
- CVE-2026-84303 · NVD
- FIRST EPSS
- GHSA-qc2q-p7wx-3px3 · GitHub Advisory Database · CC BY 4.0
- CVE-2026-84303 · Red Hat security data · CC BY 4.0
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