GHSA-6p68-w45g-48j7 Traefik has a possible vulnerability with its path matchers

• Go github.com/traefik/traefik: <= 1.7.34 (no fix yet) • Go github.com/traefik/traefik/v2: < 2.11.23 → fixed in 2.11.23 • Go github.com/traefik/traefik/v3: < 3.3.6 → fixed in 3.3.6 • Go github.com/traefik/traefik/v3: >= 3.4.0-rc1, < 3.4.0-rc2 → fixed in 3.4.0-rc2

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 `/../` 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/../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/v2.11.24 • https://github.com/traefik/traefik/releases/tag/v3.3.6 • https://github.com/traefik/traefik/releases/tag/v3.4.0-rc2 Workaround Add a `PathRegexp` rule to the matcher to prevent matching a route with a `/../` in the path. Example: ```yaml match: PathPrefix(`/service`) && !PathRegexp(`(?:(/\.\./)+.*)`) ``` For more information If you have any questions or comments about this advisory, please open an issue.