by Kastro
Paper/Archive/CVE-2026-88008

CVE-2026-88008

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

EPSS 0.5%CVSS 9.1
critical.is priorityof 100
36
CVSS 9.1 (NVD)9.1 / 10 × 3027.3Not in CISA KEV+300.0EPSS percentile 42.0.420 × 208.4No public exploit+100.0SSVC exploitation: none+100.0
Description · from the CVE record

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.

Affected

ProductAffectedFixed inSource
traefik>= 2.11.26, < 2.11.57–CNA
traefik>= 3.4.2, < 3.7.13–CNA

Scores by source

NVD9.1CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
GitHub_M (CNA)7.0CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:N/SC:H/SI:H/SA:N
CISA ADPSSVCExploitation: none · Automatable: no · Technical impact: partial

References

refgithub.com/traefik/traefik/security/advisories/GHSA-w4v4-9rw7-5326refgithub.com/traefik/traefik/pull/13797refgithub.com/traefik/traefik/commit/a277e94664ffc1ce9543df552d3bbf48d4d3b8b3refgithub.com/traefik/traefik/releases/tag/v2.11.57refgithub.com/traefik/traefik/releases/tag/v3.7.13