{"cve":"CVE-2026-33433","nvd":{"published":"2026-03-27T15:16:54.980","modified":"2026-07-15T02:20:13.380","status":"Modified","description":"Traefik is an HTTP reverse proxy and load balancer. Prior to versions 2.11.42, 3.6.11, and 3.7.0-ea.3, when `headerField` is configured with a non-canonical HTTP header name (e.g., `x-auth-user` instead of `X-Auth-User`), an authenticated attacker can inject their own canonical version of that header to impersonate any identity to the backend. The backend receives two header entries — the attacker-injected canonical one is read first, overriding Traefik's non-canonical write. Versions 2.11.42, 3.6.11, and 3.7.0-ea.3 patch the issue.","cvss_v4":{"vector":"CVSS:4.0/AV:N/AC:H/AT:P/PR:H/UI:N/VC:N/VI:N/VA:N/SC:H/SI:H/SA:N","score":5.1},"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","score":8.8},"cwes":["CWE-290"],"references":["https://github.com/traefik/traefik/releases/tag/v2.11.42","https://github.com/traefik/traefik/releases/tag/v3.6.11","https://github.com/traefik/traefik/releases/tag/v3.7.0-ea.3","https://github.com/traefik/traefik/security/advisories/GHSA-qr99-7898-vr7c","https://access.redhat.com/errata/RHSA-2026:10175"],"products":["traefik:traefik"],"source":"nvd","synced_at":"2026-10-19T22:28:18.033120106+00:00"},"epss":{"cve":"CVE-2026-33433","score":0.00487,"percentile":0.41955,"date":"2026-10-31"},"kev":null,"osv":[{"id":"GHSA-qr99-7898-vr7c","url":"https://osv.dev/vulnerability/GHSA-qr99-7898-vr7c","summary":"Traefik Vulnerable to BasicAuth/DigestAuth Identity Spoofing via Non-Canonical headerField","modified":"2026-09-10T03:51:00.751092882Z","packages":[{"ecosystem":"Go","name":"github.com/traefik/traefik/v2","purl":"pkg:golang/github.com/traefik/traefik/v2","ranges":["<2.11.42"],"fixed":["2.11.42"]},{"ecosystem":"Go","name":"github.com/traefik/traefik/v3","purl":"pkg:golang/github.com/traefik/traefik/v3","ranges":[">=3.0.0-beta1 <3.6.12"],"fixed":["3.6.12"]},{"ecosystem":"Go","name":"github.com/traefik/traefik/v3","purl":"pkg:golang/github.com/traefik/traefik/v3","ranges":[">=3.7.0-ea.1 <3.7.0-ea.3"],"fixed":["3.7.0-ea.3"]}]},{"id":"GO-2026-4893","url":"https://osv.dev/vulnerability/GO-2026-4893","summary":"Traefik Vulnerable to BasicAuth/DigestAuth Identity Spoofing via Non-Canonical headerField in github.com/traefik/traefik","modified":"2026-04-07T03:44:12.500703481Z","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":["<2.11.42"],"fixed":["2.11.42"]},{"ecosystem":"Go","name":"github.com/traefik/traefik/v3","purl":"pkg:golang/github.com/traefik/traefik/v3","ranges":[">=3.0.0-beta1 <3.6.12",">=3.7.0-ea.1 <3.7.0-ea.3"],"fixed":["3.6.12","3.7.0-ea.3"]}]}],"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."]}