# Traefik entrypoint header-name sanitization bypassed via request trailers

Advisory record · `GHSA-v67p-phpq-fc8x`

- **Identifiers:** `GHSA-v67p-phpq-fc8x` · `CVE-2026-88004` · `GO-2026-6467`
- **State:** Confirmed
- **Severity:** CVSS 7.0 High
- **Critical:** No
- **Weakness (CWE):** [CWE-436](https://cwe.mitre.org/data/definitions/436.html) · [CWE-807](https://cwe.mitre.org/data/definitions/807.html)
- **Tags:** [CWE-436](https://agentprime.io/advisories/tag/cwe-436.md) · [CWE-807](https://agentprime.io/advisories/tag/cwe-807.md)
- **Published:** 10 Sept 2026
- **Updated:** 17 Sept 2026
- **Reviewed by a person:** No

Published by the GitHub Advisory Database at 10 Sept 2026, 23:04 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

## Affected packages

- `github.com/traefik/traefik/v3` (Go): affected `>=3.2.0, <3.7.13`; fixed in `3.7.13`

## Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

> Traefik v3 versions from 3.2.0 before 3.7.13 let an unauthenticated client smuggle sanitized header names, such as X_Auth_User or X-Forwarded-Prefix, through HTTP trailers, bypassing the entrypoint's header-name sanitization. When a body-buffering middleware such as retry or buffering is in the chain, the attacker-chosen trailer value can reach the backend, and backends that merge trailers into headers may act on it. Upgrade to Traefik v3.7.13, which is the fix; end-of-life v3 lines have no separate fix and need to move to v3.7.13.

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

- 7.0 High, CVSS 4.0: `CVSS:4.0/AV:N/AC:H/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:** 0.0045, the 39th percentile, on 6 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-v67p-phpq-fc8x)

## Sources

- [GitHub Advisory Database: GHSA-v67p-phpq-fc8x](https://github.com/advisories/GHSA-v67p-phpq-fc8x)
- [OSV: GHSA-v67p-phpq-fc8x](https://osv.dev/vulnerability/GHSA-v67p-phpq-fc8x)
- <https://github.com/traefik/traefik/security/advisories/GHSA-v67p-phpq-fc8x>
- <https://nvd.nist.gov/vuln/detail/CVE-2026-88004>
- <https://github.com/traefik/traefik/pull/13822>
- <https://github.com/traefik/traefik/commit/55bbda4f65e0f9c533c870983a767a7081126db7>
- <https://github.com/traefik/traefik>
- <https://github.com/traefik/traefik/releases/tag/v3.7.13>

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-v67p-phpq-fc8x>, 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-v67p-phpq-fc8x/>. Everything for agents: <https://agentprime.io/llms.txt>.