{"id":"EUVD-2026-75429","revision":"a1dc33c1a0604b16a0ccd8549cd49d16","records":[{"revision":"a1dc33c1a0604b16a0ccd8549cd49d16","observedAt":"2026-11-09T16:08:30.03+00:00","statement":{"source":"euvd","id":"EUVD-2026-75429","aliases":["CVE-2026-88879","GHSA-cwr6-3wm2-9xhw"],"title":"Traefik is an HTTP reverse proxy and load balancer. In Traefik v1.x, v2.x through v2.11.55, and v3.0.0 through v3.7.11, header names are canonicalized only on dashes, so X-Auth-User, X_Auth_User and X.Auth.User are treated as three distinct…","description":"Traefik is an HTTP reverse proxy and load balancer. In Traefik v1.x, v2.x through v2.11.55, and v3.0.0 through v3.7.11, header names are canonicalized only on dashes, so X-Auth-User, X_Auth_User and X.Auth.User are treated as three distinct headers by Traefik, while backends that derive variable names from header names (CGI, WSGI, PHP, NGINX and others) collapse them into a single variable. A client can therefore smuggle a dot-form alias of a header that Traefik manages past the middleware managing it — for example supplying X.Authenticated.User alongside the canonical X-Authenticated-User written by the ForwardAuth middleware — causing such a backend to read the client-supplied value instead of the identity Traefik asserted. In the tested configuration (PHP 8.2 built-in SAPI over an HTTP/1 backend path), Go's lexical header ordering makes the attacker-supplied value win deterministically, so a client that ForwardAuth admits as a low-privilege identity can be treated by the backend as a different user or role. Any header Traefik sets is affected, not only ForwardAuth's. This is an incomplete fix for GHSA-x677-9fxg-v5c5, which blocked only the underscore form. Fixed in v2.11.56 and v3.7.12, which add the aliasHeadersStrategy entry-point option; because it defaults to 'keep' for backwards compatibility, it must be explicitly set to 'delete' or 'reject' for the fix to take effect. Unmaintained release lines will not receive a patch.","state":0,"publishedAt":null,"modifiedAt":null,"affected":[],"metrics":[{"system":"EUVD CVSS 4.0","vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:N/VI:N/VA:N/SC:H/SI:H/SA:N","score":5.3,"severity":null}],"references":["https://github.com/traefik/traefik/security/advisories/GHSA-rf44-j88r-hh8c","https://www.vulncheck.com/advisories/traefik-before-2.11.56-identity-spoofing-via-header-alias"],"sourceUrl":"https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-75429","license":"ENISA EUVD · source terms and attribution apply","enrichment":{"sourceStatus":null,"weaknesses":[],"productCriteria":[],"sourceDates":{"datePublished":"Sep 10, 2026, 1:05:30 PM","dateUpdated":"Oct 8, 2026, 3:25:59 PM"},"relatedAdvisories":[{"id":"RHSA-2026:90321","title":"Red Hat Security Advisory: Red Hat OpenShift Dev Spaces 3.31.0 Release.","vulnerabilityIds":["CVE-2023-54404","CVE-2025-62718","CVE-2026-8643","CVE-2026-9496","CVE-2026-12185","CVE-2026-13697","CVE-2026-14682","CVE-2026-15076","CVE-2026-16308","CVE-2026-17106","CVE-2026-18427","CVE-2026-19203","CVE-2026-19534","CVE-2026-39820","CVE-2026-41178","CVE-2026-41707","CVE-2026-42499","CVE-2026-42502","CVE-2026-45416","CVE-2026-47884","CVE-2026-47886","CVE-2026-47888","CVE-2026-47890","CVE-2026-47892","CVE-2026-50010","CVE-2026-55831","CVE-2026-55833","CVE-2026-55851","CVE-2026-56745","CVE-2026-56746","CVE-2026-56819","CVE-2026-56852","CVE-2026-56854","CVE-2026-58062","CVE-2026-59280","CVE-2026-59282","CVE-2026-59283","CVE-2026-59296","CVE-2026-59313","CVE-2026-59323","CVE-2026-59651","CVE-2026-59887","CVE-2026-59899","CVE-2026-59901","CVE-2026-62243","CVE-2026-64607","CVE-2026-67213","CVE-2026-67312","CVE-2026-67313","CVE-2026-67314","CVE-2026-67320","CVE-2026-67321","CVE-2026-68494","CVE-2026-68497","CVE-2026-69152","CVE-2026-69192","CVE-2026-71290","CVE-2026-71324","CVE-2026-71325","CVE-2026-71327","CVE-2026-73500","CVE-2026-73508","CVE-2026-74835","CVE-2026-75838","CVE-2026-75899","CVE-2026-75931","CVE-2026-76169","CVE-2026-81521","CVE-2026-82417","CVE-2026-82562","CVE-2026-84292","CVE-2026-84375","CVE-2026-84394","CVE-2026-84428","CVE-2026-84445","CVE-2026-84469","CVE-2026-84504","CVE-2026-84961","CVE-2026-85062","CVE-2026-85124","CVE-2026-85152","CVE-2026-85595","CVE-2026-85597","CVE-2026-86063","CVE-2026-87743","CVE-2026-88004","CVE-2026-88007","CVE-2026-88008","CVE-2026-88009","CVE-2026-88011","CVE-2026-88012","CVE-2026-88031","CVE-2026-88878","CVE-2026-88879","CVE-2026-90711","CVE-2026-93749","CVE-2026-100655","CVE-2026-100656","CVE-2026-100666","CVE-2026-101916","CVE-2026-102925","CVE-2026-102930","CVE-2026-103435","CVE-2026-109618","CVE-2026-109619"]}],"note":"EUVD source date text has no stated timezone and is retained without inventing a UTC instant. Related bulletin membership is not an alias, common cause or applicability claim. A missing vector with a zero score is treated as unrated. Complete vendor/product and underlying source evidence remains in the original JSON."},"key":"euvd:EUVD-2026-75429","identifiers":["EUVD-2026-75429","CVE-2026-88879","GHSA-cwr6-3wm2-9xhw"]},"retained":false,"historicalAffected":[]}],"coverage":[]}