GHSA-gm3x-23wp-hc2c

Опубликовано: 08 дек. 2025

Источник: github

Github: Прошло ревью

CVSS4: 6.9

Описание

Path Normalization Bypass in Traefik Router + Middleware Rules

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

For more information

If you have any questions or comments about this advisory, please open an issue.

Original Description

### Summary A vulnerability exists in Traefik’s path matching logic that allows attackers to bypass access-control middleware (e.g., blocking rules) by using URL-encoded paths. I found this vulnerability while playing PwnSec CTF 2025 with my team @0xL4ugh

Details

Traefik evaluates router rules before decoding or normalizing the request path, but forwards the request after decoding to the backend service. As a result, routes meant to block access to sensitive endpoints (such as internal, beta, or admin endpoints) can be trivially bypassed.

PoC

Traefik configuration used in this issue :

entryPoints = ["web"] rule = "PathPrefix(`/report_note`)" priority = 10 middlewares = ["block-access"] service = "flask-service" [http.middlewares.block-access.replacePathRegex] regex = ".*" replacement = "/blocked"

The intention is to block all access to /report_note.

However, the following request bypasses the block:

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

Impact

Access Control Bypass: Any endpoint intended to be blocked (e.g., admin/debug/beta APIs) can be accessed by URL-encoding slashes or other characters.

This could lead to:

Unauthorized access to restricted endpoints
Execution of protected internal functionality
Potential privilege escalation
Bypass of security policies enforced via Traefik routing rules

Ссылки

Пакеты

Наименование

github.com/traefik/traefik

Затронутые версииВерсия исправления

<= 1.7.34

Отсутствует

Наименование

github.com/traefik/traefik/v2

Затронутые версииВерсия исправления

< 2.11.32

2.11.32

Наименование

github.com/traefik/traefik/v3

Затронутые версииВерсия исправления

< 3.6.3

3.6.3

EPSS

Процентиль: 1%

0.00013

Низкий

6.9 Medium

CVSS4

CVE ID

CVE-2025-66490

Дефекты

CWE-436

Связанные уязвимости

CVE-2025-66490

CVSS3: 6.5

nvd

2 месяца назад

Traefik is an HTTP reverse proxy and load balancer. For versions prior to 2.11.32 and 2.11.31 through 3.6.2, requests using PathPrefix, Path or PathRegex matchers can bypass path normalization. When Traefik uses path-based routing, requests containing URL-encoded restricted characters (/, \, Null, ;, ?, #) can bypass the middleware chain and reach unintended backends. For example, a request to http://mydomain.example.com/admin%2F could reach service-a without triggering my-security-middleware, bypassing security controls for the /admin/ path. This issue is fixed in versions 2.11.32 and 3.6.3.

CVE-2025-66490

CVSS3: 6.5

debian

2 месяца назад

Traefik is an HTTP reverse proxy and load balancer. For versions prior ...

EPSS

Процентиль: 1%

0.00013

Низкий

6.9 Medium

CVSS4

CVE ID

CVE-2025-66490

Дефекты

CWE-436