GHSA-gm3x-23wp-hc2c

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

• 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.

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

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

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