Vulnerability · Published Aug 6, 2026 · Assigned by GitHub_M
CVE-2026-71324Traefik: Cross-user response poisoning via proxied CONNECT on Traefik's shared backend keep-alive pool
High 7.0
In plain English
A high-severity security flaw in traefik from traefik. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 1.1% (higher than 65% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
Traefik is an open source HTTP reverse proxy and load balancer. Prior to 2.11.53, 3.6.24, and 3.7.9, Traefik's default HTTP reverse proxy forwards a plain HTTP/2 or HTTP/3 CONNECT request and its body to an HTTP/1.1 upstream through a shared net/http.Transport. When the upstream answers the CONNECT with a keep-alive non-2xx response and does not drain the body, Traefik returns the desynchronized backend socket to its shared pool and reuses it for other clients. An unauthenticated attacker can use this behavior to make a different client read the attacker's smuggled response, which can include authenticated or private content from another request. The ForwardAuth middleware with forwardBody true and preserveRequestMethod true can re-issue a CONNECT with the buffered body attached, exposing the auth-client pool to the same desynchronization. This issue is fixed in 2.11.53, 3.6.24, and 3.7.9.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Go | github.com/traefik/traefik | no fix listed | GHSA-3ccp-42pg-hgv6 |
| Go | github.com/traefik/traefik | no fix listed | GO-2026-6201 |
| Go | github.com/traefik/traefik/v2 | 2.11.53 | GHSA-3ccp-42pg-hgv6 |
| Go | github.com/traefik/traefik/v2 | 2.11.53 | GO-2026-6201 |
| Go | github.com/traefik/traefik/v3 | 3.7.9 | GHSA-3ccp-42pg-hgv6 |
| Go | github.com/traefik/traefik/v3 | 3.6.24, 3.7.9 | GO-2026-6201 |
| Go | github.com/traefik/traefik/v3 | 3.6.24 | GHSA-3ccp-42pg-hgv6 |
Affected products (as reported)
Weakness: CWE-444 · Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:N/SC:H/SI:H/SA:N
References
- https://github.com/traefik/traefik/security/advisories/GHSA-3ccp-42pg-hgv6 x_refsource_CONFIRM
- https://github.com/traefik/traefik/pull/13542 x_refsource_MISC
- https://github.com/traefik/traefik/pull/13543 x_refsource_MISC
- https://github.com/traefik/traefik/pull/13556 x_refsource_MISC
- https://github.com/traefik/traefik/commit/04d36f28e4eae7535e96a6351dd9f7bfb48a30e7 x_refsource_MISC
- https://github.com/traefik/traefik/commit/0807b6d5dd1da8b2f7f4076ea2392b5437bf2ab0 x_refsource_MISC
- https://github.com/traefik/traefik/commit/94a7508817d180f0ab2f1eae93df48d4ab19ecce x_refsource_MISC
- https://github.com/traefik/traefik/releases/tag/v2.11.53 x_refsource_MISC
- https://github.com/traefik/traefik/releases/tag/v3.6.24 x_refsource_MISC
- https://github.com/traefik/traefik/releases/tag/v3.7.9 x_refsource_MISC