OAuth2 Proxy: Health Check User-Agent Matching Bypasses Authentication in auth_request Mode_CVE-2026-34457

{
    "lastseen": "",
    "description": "OAuth2 Proxy is a reverse proxy that provides authentication using OAuth2 providers. Versions prior to 7.15.2 contain a configuration-dependent authentication bypass in deployments where OAuth2 Proxy is used with an auth_request-style integration (such as nginx auth_request) and either --ping-user-agent is set or --gcp-healthchecks is enabled. In affected configurations, OAuth2 Proxy treats any request with the configured health check User-Agent value as a successful health check regardless of the requested path, allowing an unauthenticated remote attacker to bypass authentication and access protected upstream resources. Deployments that do not use auth_request-style subrequests or that do not enable --ping-user-agent/--gcp-healthchecks are not affected. This issue is fixed in 7.15.2.",
    "published": "2026-04-14T22:14:38.937Z",
    "modified": "2026-04-14T22:14:38.937Z",
    "type": "cve",
    "title": "OAuth2 Proxy: Health Check User-Agent Matching Bypasses Authentication in auth_request Mode",
    "source": "GitHub_M",
    "references": "https://github.com/oauth2-proxy/oauth2-proxy/security/advisories/GHSA-5hvv-m4w4-gf6v\nhttps://github.com/oauth2-proxy/oauth2-proxy/releases/tag/v7.15.2",
    "id": "CVE-2026-34457",
    "bulletinFamily": "",
    "cwe": [
        "CWE-290"
    ],
    "cvelist": null,
    "sourceData": "oauth2-proxy oauth2-proxy < 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": "",
            "attackVector": "",
            "attackComplexity": "",
            "privilegesRequired": "",
            "userInteraction": "",
            "scope": "",
            "confidentialityImpact": "",
            "integrityImpact": "",
            "availabilityImpact": ""
        }
    },
    "href": "",
    "category_name": "CVE",
    "post_link": "",
    "product": "oauth2-proxy",
    "version": "< 7.15.2",
    "vendor": "oauth2-proxy",
    "ai_description": "Authentication bypass vulnerability in OAuth2 Proxy due to incorrect health check User-Agent matching",
    "ai_severity": "Critical",
    "ai_vendor": "oauth2-proxy",
    "ai_product": "oauth2-proxy",
    "ai_version": "< 7.15.2",
    "ai_score": 9.1
}