---
id: CVE-2025-66490
title: Traefik is an HTTP reverse proxy and load balancer
summary: >-
  Traefik is an HTTP reverse proxy and load balancer. For versions prior to
  2.11.32 and 2.11.31 through 3.6.2, requests using PathPrefix, Path or
  PathRegex matchers can bypass path normalization. When Traefik uses path-based
  routing, reque…
severity: medium
cvss: 6.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N'
cwe:
  - CWE-436
vendor: traefik
product: traefik
affected:
  - traefik < 2.11.32
  - 'traefik >= 3.0.0, < 3.6.3'
patched:
  - traefik 3.6.3
published: '2025-12-09'
updated: '2026-10-14'
sourceUpdated: '2026-10-14T22:10:00.210'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2025-66490'
references:
  - url: 'https://github.com/traefik/traefik/releases/tag/v2.11.32'
    label: security-advisories@github.com
  - url: 'https://github.com/traefik/traefik/releases/tag/v3.6.4'
    label: security-advisories@github.com
  - url: 'https://github.com/traefik/traefik/security/advisories/GHSA-gm3x-23wp-hc2c'
    label: security-advisories@github.com
  - url: 'https://github.com/traefik/traefik/security/advisories/GHSA-gm3x-23wp-hc2c'
    label: 134c704f-9b21-4f2e-91b3-4a467353bcc0
tags:
  - nvd
epss: 0.00439
epssPercentile: 0.36585
ingestedAt: '2026-10-14T23:00:02.029Z'
---

## Overview

Traefik is an HTTP reverse proxy and load balancer. For versions prior to 2.11.32 and 2.11.31 through 3.6.2, requests using PathPrefix, Path or PathRegex matchers can bypass path normalization. When Traefik uses path-based routing, requests containing URL-encoded restricted characters (/, \, Null, ;, ?, #) can bypass the middleware chain and reach unintended backends. For example, a request to http://mydomain.example.com/admin%2F could reach service-a without triggering my-security-middleware, bypassing security controls for the /admin/ path. This issue is fixed in versions 2.11.32 and 3.6.3.

## Affected

- `traefik < 2.11.32`
- `traefik >= 3.0.0, < 3.6.3`

## Remediation

Upgrade past the affected range:

- `traefik 3.6.3`