# Path Normalization Bypass in Traefik Router + Middleware Rules

Advisory record · `GHSA-gm3x-23wp-hc2c`

- **Identifiers:** `GHSA-gm3x-23wp-hc2c` · `CVE-2025-66490` · `GO-2025-4206`
- **State:** Confirmed
- **Severity:** CVSS 6.9 Medium
- **Critical:** No
- **Weakness (CWE):** [CWE-436](https://cwe.mitre.org/data/definitions/436.html)
- **Tags:** [CWE-436](https://agentprime.io/advisories/tag/cwe-436.md)
- **Published:** 8 Dec 2025
- **Updated:** 16 Apr 2026
- **Reviewed by a person:** No

Published by the GitHub Advisory Database at 8 Dec 2025, 16:42 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

## Affected packages

- `github.com/traefik/traefik` (Go): affected `<=1.7.34`; no fixed version yet
- `github.com/traefik/traefik/v2` (Go): affected `<2.11.32`; fixed in `2.11.32`
- `github.com/traefik/traefik/v3` (Go): affected `<3.6.3`; fixed in `3.6.3`

## 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

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

- **CISA KEV:** Not listed.
- **EPSS:** 0.0044, the 38th percentile, on 8 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

## Timeline

- 31 Oct 2026, 15:08 UTC: First seen by agentprime
- 31 Oct 2026, 15:08 UTC: [Confirmed by OSV](https://osv.dev/vulnerability/GHSA-gm3x-23wp-hc2c)

## Sources

- [GitHub Advisory Database: GHSA-gm3x-23wp-hc2c](https://github.com/advisories/GHSA-gm3x-23wp-hc2c)
- [OSV: GHSA-gm3x-23wp-hc2c](https://osv.dev/vulnerability/GHSA-gm3x-23wp-hc2c)
- <https://github.com/traefik/traefik/security/advisories/GHSA-gm3x-23wp-hc2c>
- <https://nvd.nist.gov/vuln/detail/CVE-2025-66490>
- <https://github.com/traefik/traefik>
- <https://github.com/traefik/traefik/releases/tag/v2.11.32>
- <https://github.com/traefik/traefik/releases/tag/v3.6.4>

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-gm3x-23wp-hc2c>, 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-gm3x-23wp-hc2c/>. Everything for agents: <https://agentprime.io/llms.txt>.