CVE-2026-88008

critical

Traefik is an open source HTTP reverse proxy and load balancer.

Vendor / product: Traefik — traefik

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.

CVSS

9.1

9.1 (CVSS v3.1)

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

Severity source: NVD CVSS v3.1 (nvd@nist.gov)

Timeline (UTC)

Published: 2026-09-10 15:17

Modified: 2026-09-14 19:59

NVD status: Analyzed

Last synced 1 day ago

Verified against the source API 2026-10-27 07:07 UTC

Exploitation

Not listed in CISA KEV (as of last catalog sync)

Absence from KEV does not mean a CVE is not exploited. Exploitation status: unknown (no authoritative evidence in our sources).

Affected products

traefik / traefik ≥2.11.26 <2.11.57, ≥3.4.2 <3.7.13

Weakness classification (CWE)

CWE-444 CWE-863

Source: NVD / CISA. “NVD-CWE-Other” and “NVD-CWE-noinfo” mean NVD could not assign a specific weakness.

Mitigation & advisories

Vendor advisory: https://github.com/traefik/traefik/security/advisories/GHSA-w4v4-9rw7-5326

Patch / mitigation: https://github.com/traefik/traefik/commit/a277e94664ffc1ce9543df552d3bbf48d4d3b8b3

Patch / mitigation: https://github.com/traefik/traefik/pull/13797

Patch / mitigation: https://github.com/traefik/traefik/security/advisories/GHSA-w4v4-9rw7-5326

References

https://github.com/traefik/traefik/commit/a277e94664ffc1ce9543df552d3bbf48d4d3b8b3 security-advisories@github.com
https://github.com/traefik/traefik/pull/13797 security-advisories@github.com
https://github.com/traefik/traefik/releases/tag/v2.11.57 security-advisories@github.com
https://github.com/traefik/traefik/releases/tag/v3.7.13 security-advisories@github.com
https://github.com/traefik/traefik/security/advisories/GHSA-w4v4-9rw7-5326 security-advisories@github.com

Data sources

NVD CVE API 2.0 — fetched 2026-10-27 07:07 UTC · record ↗

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CVE-2026-88008

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