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CVE-2026-88008GHSA-W4V4-9RW7-5326GO-2026-6468

Traefik: Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling') and Incorrect Authorization

Published
Last modified
published
Not listed in CISA KEV
Fix
Fixed in 2.11.57, 3.7.13
1 proof of concept on GitHub
  • Exploitation: none
  • Automatable: no
  • Technical impact: partial

Summary

Traefik is an open source HTTP reverse proxy and load balancer. From 2.11.26 until 2.11.57 and 3.7.13, Traefik forwards a client-supplied Connection header requesting Upgrade, the Upgrade: h2c token, and HTTP2-Settings to a shared backend. If the backend accepts h2c and returns 101 Switching Protocols, Traefik enters a raw tunnel and no longer applies routers, BasicAuth, ForwardAuth, IPAllowList, RateLimit, access logging, metrics, or tracing to later HTTP/2 requests, allowing an unauthenticated request through an unprotected route to reach protected paths on the same backend. This issue is fixed in 2.11.57 and 3.7.13.

Timeline

  1. CVE published
  2. CISA SSVC assessment

    Exploitation: none · Automatable: no · Technical impact: partial

  3. Record last updated

Affected versions

  • traefik traefik

    From 2.11.26 · fixed in 2.11.57; From 3.4.2 · fixed in 3.7.13

  • github.com/traefik/traefik/v3Go

    From 3.4.2 · fixed in 3.7.13

  • github.com/traefik/traefik/v2Go

    From 2.11.26 · fixed in 2.11.57

  • github.com/traefik/traefikGo

    All versions

References 6

GitHub · traefik/traefik

GitHub · Boreas37/CVE-2026-88008-PoC