CVE-2026-88008
Critical- Published
- Sep 10, 2026
- Updated
- Sep 14, 2026
- Vendor
- Traefik
- Affected versions
- See affected products
- Weakness
- CWE-444, CWE-863
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.
Severity
Critical (9.1)CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
CVSS v4.0 (7.0)
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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Affected products
- Traefik Traefik >= 2.11.26, < 2.11.57
- Traefik Traefik >= 3.4.2, < 3.7.13
Exploitation status
Unknown
Technical details
Technical analysis has not been written for this record yet.
Mitigation & remediation
Follow the vendor advisory linked below for patches and workarounds.