GHSA-vrch-868g-9jx5 — Traefik allows path traversal using url encoding

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

## 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 URL contains a URL encoded string in its path, 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(‘/service’) kind: Rule services: - name: service-a port: 8080 middlewares: - name: my-middleware-a - match: PathPrefix(‘/service/sub-path’) kind: Rule services: - name: service-a port: 8080 ```

In such a case, the request `http://mydomain.example.com/service/sub-path/%2e%2e/other-path` will reach the backend `my-service-a` without operating the middleware `my-middleware-a` unless the computed path is `http://mydomain.example.com/service/other-path` and should be computes by the first router (operating `my-middleware-a`).

## Patches

- https://github.com/traefik/traefik/releases/tag/v2.11.25 - https://github.com/traefik/traefik/releases/tag/v3.4.1

## For more information

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

<details> <summary>Original Description</summary> ### Summary

Path traversal with "/..…

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GHSA-vrch-868g-9jx5 — Traefik allows path traversal using url encoding