{"document":{"category":"csaf_vex","csaf_version":"2.0","title":"CVE-2026-33433: Traefik Vulnerable to BasicAuth/DigestAuth Identity Spoofing via Non-Canonical headerField","publisher":{"category":"vendor","name":"HarborGuard Database","namespace":"https://database.harborguard.co"},"tracking":{"id":"CVE-2026-33433","status":"final","version":"1","initial_release_date":"2026-03-27T13:49:08.455Z","current_release_date":"2026-06-30T03:16:46.639Z","revision_history":[{"date":"2026-03-27T13:49:08.455Z","number":"1","summary":"Initial machine-readable export from HarborGuard."}]},"distribution":{"tlp":{"label":"WHITE"},"text":"Public CVE data; freely redistributable."},"notes":[{"category":"description","text":"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.","title":"CVE description"}],"references":[{"category":"self","summary":"CVE-2026-33433 on HarborGuard Database","url":"https://database.harborguard.co/cve/CVE-2026-33433"},{"category":"external","summary":"CVE Record","url":"https://www.cve.org/CVERecord?id=CVE-2026-33433"},{"category":"external","summary":"https://github.com/traefik/traefik/security/advisories/GHSA-qr99-7898-vr7c","url":"https://github.com/traefik/traefik/security/advisories/GHSA-qr99-7898-vr7c"},{"category":"external","summary":"https://github.com/traefik/traefik/releases/tag/v2.11.42","url":"https://github.com/traefik/traefik/releases/tag/v2.11.42"},{"category":"external","summary":"https://github.com/traefik/traefik/releases/tag/v3.6.11","url":"https://github.com/traefik/traefik/releases/tag/v3.6.11"},{"category":"external","summary":"https://github.com/traefik/traefik/releases/tag/v3.7.0-ea.3","url":"https://github.com/traefik/traefik/releases/tag/v3.7.0-ea.3"}]},"product_tree":{"branches":[{"category":"vendor","name":"traefik","branches":[{"category":"product_name","name":"traefik","branches":[{"category":"product_version","name":"< 2.11.42","product":{"name":"traefik traefik < 2.11.42","product_id":"CSAFPID-1","product_identification_helper":{"cpe":"cpe:2.3:a:traefik:traefik:*:*:*:*:*:*:*:*"}}},{"category":"product_version","name":">= 3.0.0-beta1, < 3.6.11","product":{"name":"traefik traefik >= 3.0.0-beta1, < 3.6.11","product_id":"CSAFPID-2","product_identification_helper":{"cpe":"cpe:2.3:a:traefik:traefik:*:*:*:*:*:*:*:*"}}},{"category":"product_version","name":">= 3.7.0-ea.1, < 3.7.0-ea.3","product":{"name":"traefik traefik >= 3.7.0-ea.1, < 3.7.0-ea.3","product_id":"CSAFPID-3","product_identification_helper":{"cpe":"cpe:2.3:a:traefik:traefik:*:*:*:*:*:*:*:*"}}}]}]}]},"vulnerabilities":[{"cve":"CVE-2026-33433","title":"Traefik Vulnerable to BasicAuth/DigestAuth Identity Spoofing via Non-Canonical headerField","notes":[{"category":"description","text":"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.","title":"CVE description"}],"product_status":{"known_affected":["CSAFPID-1","CSAFPID-2","CSAFPID-3"]},"scores":[{"cvss_v3":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:C/C:H/I:H/A:N","baseScore":7.7,"baseSeverity":"HIGH"},"products":["CSAFPID-1","CSAFPID-2","CSAFPID-3"]}],"remediations":[{"category":"none_available","details":"No fixed version is published yet. Monitor the upstream advisory.","product_ids":["CSAFPID-1","CSAFPID-2","CSAFPID-3"]}]}]}