{"cve":"CVE-2026-88011","nvd":{"published":"2026-09-10T16:18:07.933","modified":"2026-09-15T15:17:24.163","status":"Analyzed","description":"Traefik is an open source HTTP reverse proxy and load balancer. Prior to 2.11.56, and from 3.0.0 until 3.7.12, a client-supplied dot-form header such as X.Authenticated.User survives ForwardAuth replacement and underscoreHeadersStrategy because Go treats it as distinct from X-Authenticated-User while normalization-prone CGI, WSGI, PHP, and NGINX backends collapse both names. A backend can consequently consume the client value instead of the identity Traefik asserted, allowing identity spoofing for any header managed by Traefik. The aliasHeadersStrategy protection is disabled by default and must be configured as delete or reject. The mitigation is available in 2.11.56 and 3.7.12.","cvss_v4":{"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},"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N","score":8.1},"cwes":["CWE-290"],"references":["https://github.com/traefik/traefik/commit/0331801c72329e0eaeb850e53ccce87c57fbecf8","https://github.com/traefik/traefik/pull/13720","https://github.com/traefik/traefik/releases/tag/v2.11.56","https://github.com/traefik/traefik/releases/tag/v3.7.12","https://github.com/traefik/traefik/security/advisories/GHSA-rf44-j88r-hh8c"],"products":["traefik:traefik"],"source":"nvd","synced_at":"2026-10-19T22:52:53.108888569+00:00"},"epss":{"cve":"CVE-2026-88011","score":0.0042,"percentile":0.36326,"date":"2026-10-31"},"kev":null,"osv":[{"id":"GHSA-rf44-j88r-hh8c","url":"https://osv.dev/vulnerability/GHSA-rf44-j88r-hh8c","summary":"Traefik: ForwardAuth identity spoofing via dot-form header alias","modified":"2026-09-17T17:40:34.771461848Z","packages":[{"ecosystem":"Go","name":"github.com/traefik/traefik/v2","purl":"pkg:golang/github.com/traefik/traefik/v2","ranges":["<2.11.56"],"fixed":["2.11.56"]},{"ecosystem":"Go","name":"github.com/traefik/traefik/v3","purl":"pkg:golang/github.com/traefik/traefik/v3","ranges":[">=3.0.0 <3.7.12"],"fixed":["3.7.12"]}]},{"id":"GO-2026-6455","url":"https://osv.dev/vulnerability/GO-2026-6455","summary":"Traefik: ForwardAuth identity spoofing via dot-form header alias in github.com/traefik/traefik","modified":"2026-09-17T17:40:34.771461848Z","packages":[{"ecosystem":"Go","name":"github.com/traefik/traefik","purl":"pkg:golang/github.com/traefik/traefik","ranges":["all versions"],"fixed":[]},{"ecosystem":"Go","name":"github.com/traefik/traefik/v2","purl":"pkg:golang/github.com/traefik/traefik/v2","ranges":["<2.11.56"],"fixed":["2.11.56"]},{"ecosystem":"Go","name":"github.com/traefik/traefik/v3","purl":"pkg:golang/github.com/traefik/traefik/v3","ranges":[">=3.0.0 <3.7.12"],"fixed":["3.7.12"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}