OAuth2 Proxy has an Authentication Bypass via X-Forwarded-Uri Header Spoofing_CVE-2026-40575

{
    "lastseen": "",
    "description": "OAuth2 Proxy is a reverse proxy that provides authentication using OAuth2 providers. Versions 7.5.0 through 7.15.1 may trust a client-supplied `X-Forwarded-Uri` header when `--reverse-proxy` is enabled and `--skip-auth-regex` or `--skip-auth-route` is configured. An attacker can spoof this header so OAuth2 Proxy evaluates authentication and skip-auth rules against a different path than the one actually sent to the upstream application. This can result in an unauthenticated remote attacker bypassing authentication and accessing protected routes without a valid session. Impacted users are deployments that run oauth2-proxy with `--reverse-proxy` enabled and configure at least one `--skip-auth-regex` or `--skip-auth-route` rule. This issue is patched in `v7.15.2`. Some workarounds are available for those who cannot upgrade immediately. Strip any client-provided `X-Forwarded-Uri` header at the reverse proxy or load balancer level; explicitly overwrite `X-Forwarded-Uri` with the actual request URI before forwarding requests to OAuth2 Proxy; restrict direct client access to OAuth2 Proxy so it can only be reached through a trusted reverse proxy; and/or remove or narrow `--skip-auth-regex` / `--skip-auth-route` rules where possible. For nginx-based deployments, ensure `X-Forwarded-Uri` is set by nginx and not passed through from the client.",
    "published": "2026-04-21T23:20:30.486Z",
    "modified": "2026-04-21T23:20:30.486Z",
    "type": "cve",
    "title": "OAuth2 Proxy has an Authentication Bypass via X-Forwarded-Uri Header Spoofing",
    "source": "GitHub_M",
    "references": "https://github.com/oauth2-proxy/oauth2-proxy/security/advisories/GHSA-7x63-xv5r-3p2x",
    "id": "CVE-2026-40575",
    "bulletinFamily": "",
    "cwe": [
        "CWE-290"
    ],
    "cvelist": null,
    "sourceData": "oauth2-proxy oauth2-proxy >= 7.5.0, < 7.15.2",
    "sourceHref": "",
    "cvss": {
        "score": 9.1,
        "severity": "CRITICAL",
        "vector": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N",
        "version": "3.1"
    },
    "cvss2": [],
    "cvss3": {
        "version": "",
        "vectorString": "",
        "baseScore": 0,
        "baseSeverity": "",
        "attackVector": "",
        "attackComplexity": "",
        "privilegesRequired": "",
        "userInteraction": "",
        "scope": "",
        "confidentialityImpact": "",
        "integrityImpact": "",
        "availabilityImpact": "",
        "cvssV3": {
            "version": "",
            "vectorString": "",
            "baseScore": 0,
            "baseSeverity": "",
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            "privilegesRequired": "",
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            "confidentialityImpact": "",
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        }
    },
    "href": "",
    "category_name": "CVE",
    "post_link": "",
    "product": "oauth2-proxy",
    "version": ">= 7.5.0, < 7.15.2",
    "vendor": "oauth2-proxy",
    "ai_description": "OAuth2 Proxy is vulnerable to an authentication bypass via X-Forwarded-Uri header spoofing, allowing unauthenticated remote attackers to access protected routes without a valid session.",
    "ai_severity": "Critical",
    "ai_vendor": "oauth2-proxy",
    "ai_product": "OAuth2 Proxy",
    "ai_version": "7.5.0-7.15.1",
    "ai_score": 9.1
}