GHSA-gm3x-23wp-hc2c — Path Normalization Bypass in Traefik Router + Middleware Rules

2026-10-05T17:35:36.115515+00:00

Affected: Go: github.com/traefik/traefik, Go: github.com/traefik/traefik/v2, Go: github.com/traefik/traefik/v3

## 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/’) 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

- https://github.com/traefik/traefik/releases/tag/v2.11.32 - https://github.com/traefik/traefik/releases/tag/v3.6.4

## For more information

If you have any questions or comments about this advisory, please [open an issue](https://github.com/traefik/traefik/issues).

Original Description

### Summary A vulnerability exists in Traefik’s path matching logic that allows attackers…

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GHSA-gm3x-23wp-hc2c — Path Normalization Bypass in Traefik Router + Middleware Rules