# gRPC-Go: xDS RBAC HTTP Filter bypass via mixed-case Header Matching and gRFC A41 validation evasion Advisory record · `GHSA-qc2q-p7wx-3px3` - **Identifiers:** `GHSA-qc2q-p7wx-3px3` · `CVE-2026-84303` · `GO-2026-6441` - **State:** Confirmed - **Severity:** CVSS 6.3 Medium - **Critical:** No - **Weakness (CWE):** [CWE-178](https://cwe.mitre.org/data/definitions/178.html) · [CWE-863](https://cwe.mitre.org/data/definitions/863.html) - **Tags:** [Broken access control](https://agentprime.io/advisories/tag/access-control.md) · [CWE-178](https://agentprime.io/advisories/tag/cwe-178.md) - **Published:** 8 Sept 2026 - **Updated:** 15 Sept 2026 - **Reviewed by a person:** No Published by the GitHub Advisory Database at 8 Sept 2026, 20:50 UTC. agentprime has not analysed this yet, so whether it affects any app is not known. ## Affected packages - `google.golang.org/grpc` (Go): affected `<1.83.1`; fixed in `1.83.1` ## 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. Written 1 Nov 2026. ## 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 - 6.3 Medium, CVSS 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`, from 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](https://osv.dev/vulnerability/GHSA-qc2q-p7wx-3px3) ## Sources - [GitHub Advisory Database: GHSA-qc2q-p7wx-3px3](https://github.com/advisories/GHSA-qc2q-p7wx-3px3) - [OSV: GHSA-qc2q-p7wx-3px3](https://osv.dev/vulnerability/GHSA-qc2q-p7wx-3px3) - - - - - - - - Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code. ## Check whether this affects you A Match means an installed version is in the affected range above. Most don’t affect the app; agentprime hasn’t analysed this one yet. - With the agentprime MCP server (), ask your agent to check the project: `check_lockfile` sends a lockfile, `check_packages` a list of installed packages, and both return the Matches and the upgrades that clear them. `get_advisory` returns this record. Setup: - In a browser: reads your lockfile in the browser, never uploading it. - Whether it touches your code, with file and line: the Claude Code plugin, - As JSON: , or `POST https://api.agentprime.io/v1/match` with your packages () --- The web page: . Everything for agents: .