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OpenAdvisories
Medium · 6.9 CVE-2025-66490 EUVD-2025-201731GHSA-gm3x-23wp-hc2cGO-2025-4206

Traefik doesn't Prevent Path Normalization Bypass in Router + Middleware Rules

Published Dec 9, 2025 · Updated Dec 9, 2025 · Assigned by GitHub_M

Description

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 products

VendorProductAffectedFixed
traefik traefik github.com/traefik/traefik/v3 < 3.6.3, github.com/traefik/traefik/v2 < 2.11.32, github.com/traefik/traefik <= 1.7.34 —

Fixed in Linux distributions

Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.

ReleasePackageFixed inAdvisory
openSUSE Tumbleweed traefik 3.6.6-1.1 openSUSE-SU-2026:10020-1
openSUSE Tumbleweed traefik2 2.11.35-1.1 openSUSE-SU-2026:10143-1
openSUSE Leap 16.0 govulncheck-vulndb 0.0.20260723T184607-160000.1.1 openSUSE-SU-2026:21483-1
openSUSE Leap 15.6 govulncheck-vulndb 0.0.20251230T014957-150000.1.134.1 SUSE-SU-2026:0037-1

Wolfi

ReleasePackageFixed inAdvisory
Wolfi rolling traefik-3.4 No fix yet —

Affected packages

EcosystemPackageAffectedFixedRecord
Go github.com/traefik/traefik <= 1.7.34 — GHSA-gm3x-23wp-hc2c
Go github.com/traefik/traefik all versions — GO-2025-4206
Go github.com/traefik/traefik/v2 < 2.11.32 2.11.32 GHSA-gm3x-23wp-hc2c
Go github.com/traefik/traefik/v3 < 3.6.3 3.6.3 GHSA-gm3x-23wp-hc2c

Advisories 4

References