# Traefik: Incomplete fix for CVE-2026-33433 + CVE-2026-39858 cross-cohort: headerField underscore-variant identity spoofing in BasicAuth / DigestAuth / ForwardAuth

Advisory record · `GHSA-x677-9fxg-v5c5`

- **Identifiers:** `GHSA-x677-9fxg-v5c5` · `CVE-2026-54763` · `GO-2026-6211`
- **State:** Confirmed
- **Severity:** CVSS 7.8 High
- **Critical:** No
- **Weakness (CWE):** [CWE-178](https://cwe.mitre.org/data/definitions/178.html) · [CWE-290](https://cwe.mitre.org/data/definitions/290.html) · [CWE-345](https://cwe.mitre.org/data/definitions/345.html)
- **Tags:** [Authentication bypass](https://agentprime.io/advisories/tag/auth-bypass.md) · [CWE-178](https://agentprime.io/advisories/tag/cwe-178.md) · [CWE-345](https://agentprime.io/advisories/tag/cwe-345.md)
- **Published:** 6 Aug 2026
- **Updated:** 18 Aug 2026
- **Reviewed by a person:** No

Published by the GitHub Advisory Database at 6 Aug 2026, 16:53 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

## Affected packages

- `github.com/traefik/traefik/v2` (Go): affected `<2.11.51`; fixed in `2.11.51`
- `github.com/traefik/traefik/v3` (Go): affected `<3.6.22 || >=3.7.0, <3.7.6`; fixed in `3.6.22`, `3.7.6`

## 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

- 7.8 High, CVSS 4.0: `CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:H/SI:H/SA:N`, from CNA (GitHub_M)

- **CISA KEV:** Not listed.
- **EPSS:** 0.0024, the 15th percentile, on 5 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

## Timeline

- 31 Oct 2026, 14:50 UTC: First seen by agentprime
- 31 Oct 2026, 14:50 UTC: [Confirmed by OSV](https://osv.dev/vulnerability/GHSA-x677-9fxg-v5c5)

## Sources

- [GitHub Advisory Database: GHSA-x677-9fxg-v5c5](https://github.com/advisories/GHSA-x677-9fxg-v5c5)
- [OSV: GHSA-x677-9fxg-v5c5](https://osv.dev/vulnerability/GHSA-x677-9fxg-v5c5)
- <https://github.com/traefik/traefik/security/advisories/GHSA-x677-9fxg-v5c5>
- <https://nvd.nist.gov/vuln/detail/CVE-2026-54763>
- <https://github.com/traefik/traefik/pull/13262>
- <https://github.com/traefik/traefik/commit/108a5264473a2cbc8f12d6d691a3c6553cdf2c1b>
- <https://github.com/traefik/traefik>
- <https://github.com/traefik/traefik/releases/tag/v2.11.51>
- <https://github.com/traefik/traefik/releases/tag/v3.6.22>
- <https://github.com/traefik/traefik/releases/tag/v3.7.6>

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 (<https://api.agentprime.io/mcp>), 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: <https://agentprime.io/mcp.md>
- In a browser: <https://agentprime.io/check/> reads your lockfile in the browser, never uploading it.
- Whether it touches your code, with file and line: the Claude Code plugin, <https://agentprime.io/plugin.md>
- As JSON: <https://api.agentprime.io/v1/advisories/GHSA-x677-9fxg-v5c5>, or `POST https://api.agentprime.io/v1/match` with your packages (<https://agentprime.io/api.md>)

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The web page: <https://agentprime.io/advisories/GHSA-x677-9fxg-v5c5/>. Everything for agents: <https://agentprime.io/llms.txt>.