Lack of data validation - Path Traversal In github.com/traefik/traefik
Description
Traefik allows path traversal using url encoding
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
apiVersion: traefik.io/v1alpha1 kind: IngressRoute metadata: name: my-service spec: routes: - match: PathPrefix(‘/service’) kind: Rule...
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
For more information
If you have any questions or comments about this advisory, please open an issue.
Original Description
### SummaryPath traversal with "/../" using URL encodings ("/%2e%2e") allows for circumventing routing rules.
Details
When having defined a route, you can path traverse using the URL encoded variant of /../ and reach endpoints that are not made publicly available. This issue has been found and fixed earlier with regular /../ and has been fixed in this CVE. This URL encoding trick works around that https://nvd.nist.gov/vuln/detail/CVE-2025-32431
Simply implementing a check on the URL encoding won't be sufficient as path traversal can take numerous formats. See examples here: https://book.hacktricks.wiki/en/pentesting-web/file-inclusion/index.html
PoC
Setup a service with two endpoints: "/public" and "/private", which returns a 200 OK for both Setup a Traefik proxy with a single route which points to the service using path /public
Regular requests to traefik /public will return 200 OK and to /private should return 404 (response by Traefik) When making a request to /public/%2e%2e/private you should receive a 200 OK.
Impact
Impacts all traefik implementations with path prefix routes that expose only part of the downstream api
Suggestion
Provide configuration property which disables all path traversals. Steps:
Decode URL
Evaluate and construct relative path (do traversal before route evaluation)
Compare relative/evaluated path to configured routes (PathPrefix/pathRegexp)
Mitigation
Update Impact
Minimal update. May introduce new vulnerabilities or breaking changes.
Ecosystem | Component | Affected version | Patched versions |
|---|---|---|---|
 go | 2.0.0-alpha1+incompatible | ||
go | 3.4.1 | ||
go | 2.11.25 |
Aliases
References