Your RSA-2048 keys break in 2030. Find every one of them before attackers do.
🐹 Go

GHSA-gm3x-23wp-hc2c

Path Normalization Bypass in Traefik Router + Middleware Rules

Also known asCVE-2025-66490GO-2025-4206
Published
Dec 8, 2025
Updated
Apr 16, 2026
Affected
3 pkgs
Patched
2 / 3
Exploits
None indexed

EPSS Exploitation Probability

via FIRST.org ↗
0.3%probability of exploitation in next 30 days
Lower Risk25th percentile+0.31%
0.00%0.28%0.55%0.83%0.0%0.3%Jan 26Apr 26Jun 26

EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.

Blast Radius

3 pkgs affected
🐹github.com/traefik/traefik🐹github.com/traefik/traefik/v2🐹github.com/traefik/traefik/v3

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.

Description

Impact

There is a potential vulnerability in Traefik managing the requests using a PathPrefix, Path or PathRegex matcher.

When Traefik is configured to route the requests to a backend using a matcher based on the path; if the request path contains an encoded restricted character from the following set ('/', '', 'Null', ';', '?', '#'), it’s possible to target a backend, exposed using another router, by-passing the middlewares chain.

Example

apiVersion: traefik.io/v1alpha1
kind: IngressRoute
metadata:
  name: my-service
spec:
  routes:
    - match: PathPrefix(‘/admin/’)
      kind: Rule
      services:
        - name: service-a
          port: 8080
      middlewares:
        - name: my-security-middleware
    - match: PathPrefix(‘/’)
      kind: Rule
      services:
        - name: service-a
          port: 8080

In such a case, the request http://mydomain.example.com/admin%2F will reach the backend service-a without operating the middleware my-security-middleware and passing the security put in place for the /admin/ path.

Patches

For more information

If you have any questions or comments about this advisory, please open an issue.

<details> <summary>Original Description</summary>### Summary A vulnerability exists in Traefik’s path matching logic that allows attackers to bypass access-control middleware (e.g., blocking rules) by using URL-encoded paths. I found this vulnerability while playing PwnSec CTF 2025 with my team @0xL4ugh

Details

Traefik evaluates router rules before decoding or normalizing the request path, but forwards the request after decoding to the backend service. As a result, routes meant to block access to sensitive endpoints (such as internal, beta, or admin endpoints) can be trivially bypassed.

PoC

Traefik configuration used in this issue :

  entryPoints = ["web"]
  rule = "PathPrefix(`/report_note`)"
  priority = 10
  middlewares = ["block-access"]
  service = "flask-service"

[http.middlewares.block-access.replacePathRegex]
  regex = ".*"
  replacement = "/blocked"

The intention is to block all access to /report_note.

However, the following request bypasses the block:

POST /%2freport_note HTTP/1.1
Host: localhost:62814

Impact

Access Control Bypass: Any endpoint intended to be blocked (e.g., admin/debug/beta APIs) can be accessed by URL-encoding slashes or other characters.

This could lead to:

  • Unauthorized access to restricted endpoints
  • Execution of protected internal functionality
  • Potential privilege escalation
  • Bypass of security policies enforced via Traefik routing rules
</details>

Affected Packages

3 total 2 fixed
EcosystemPackageVulnerable rangeFix
🐹Gogithub.com/traefik/traefikall versionsNo fix
🐹Gogithub.com/traefik/traefik/v2all versions2.11.32
🐹Gogithub.com/traefik/traefik/v3all versions3.6.3

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/traefik/traefik. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.

  2. Fix

    No patched version of github.com/traefik/traefik has shipped for GHSA-gm3x-23wp-hc2c yet. Where your build allows, override or pin the dependency away from the vulnerable range, and apply any maintainer-recommended mitigation.

  3. Workarounds

    If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

  4. How O3 protects you

    O3 pinpoints whether GHSA-gm3x-23wp-hc2c is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Tailored to GHSA-gm3x-23wp-hc2c. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

## Impact There is a potential vulnerability in Traefik managing the requests using a `PathPrefix`, `Path` or `PathRegex` matcher. When Traefik is configured to route the requests to a backend using a matcher based on the path; if the request path contains an encoded restricted character from the following set **('/', '\', 'Null', ';', '?', '#')**, it’s possible to target a backend, exposed using another router, by-passing the middlewares chain. ## Example ```yaml apiVersion: traefik.io/v1alpha1 kind: IngressRoute metadata: name: my-service spec: routes: - match: PathPrefix(‘/admin
O3 Security · Impact-Aware SCA

Is GHSA-gm3x-23wp-hc2c in your dependencies?

O3 detects GHSA-gm3x-23wp-hc2c across Go dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.

Scan my dependencies How O3 SCA works