Traefik Vulnerable to BasicAuth/DigestAuth Identity Spoofing via Non-Canonical headerField_CVE-2026-33433

{
    "lastseen": "",
    "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 \u2014 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.",
    "published": "2026-03-27T13:49:08.455Z",
    "modified": "2026-03-30T12:00:41.940Z",
    "type": "cve",
    "title": "Traefik Vulnerable to BasicAuth/DigestAuth Identity Spoofing via Non-Canonical headerField",
    "source": "GitHub_M",
    "references": "https://github.com/traefik/traefik/security/advisories/GHSA-qr99-7898-vr7c\nhttps://github.com/traefik/traefik/releases/tag/v2.11.42\nhttps://github.com/traefik/traefik/releases/tag/v3.6.11\nhttps://github.com/traefik/traefik/releases/tag/v3.7.0-ea.3",
    "id": "CVE-2026-33433",
    "bulletinFamily": "",
    "cwe": [
        "CWE-290"
    ],
    "cvelist": null,
    "sourceData": "traefik traefik < 2.11.42\ntraefik traefik >= 3.0.0-beta1, < 3.6.11\ntraefik traefik >= 3.7.0-ea.1, < 3.7.0-ea.3",
    "sourceHref": "",
    "cvss": {
        "score": 5.1,
        "severity": "MEDIUM",
        "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",
        "version": "4.0"
    },
    "cvss2": [],
    "cvss3": {
        "version": "",
        "vectorString": "",
        "baseScore": 0,
        "baseSeverity": "",
        "attackVector": "",
        "attackComplexity": "",
        "privilegesRequired": "",
        "userInteraction": "",
        "scope": "",
        "confidentialityImpact": "",
        "integrityImpact": "",
        "availabilityImpact": "",
        "cvssV3": {
            "version": "",
            "vectorString": "",
            "baseScore": 0,
            "baseSeverity": "",
            "attackVector": "",
            "attackComplexity": "",
            "privilegesRequired": "",
            "userInteraction": "",
            "scope": "",
            "confidentialityImpact": "",
            "integrityImpact": "",
            "availabilityImpact": ""
        }
    },
    "href": "",
    "category_name": "CVE",
    "post_link": "",
    "product": "traefik",
    "version": "< 2.11.42",
    "vendor": "traefik",
    "ai_description": "",
    "ai_severity": "",
    "ai_vendor": "",
    "ai_product": "",
    "ai_version": "",
    "ai_score": 0
}