{"id":"CVE-2026-40575","summary":"OAuth2 Proxy has an Authentication Bypass via X-Forwarded-Uri Header Spoofing","details":"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.","aliases":["BIT-oauth2-proxy-2026-40575","GHSA-7x63-xv5r-3p2x","GO-2026-5236"],"modified":"2026-07-31T18:30:29.113040928Z","published":"2026-04-21T23:20:30.486Z","related":["openSUSE-SU-2026:21483-1"],"database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/40xxx/CVE-2026-40575.json","cna_assigner":"GitHub_M","cwe_ids":["CWE-290"]},"references":[{"type":"WEB","url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-40575.json"},{"type":"ADVISORY","url":"https://access.redhat.com/security/cve/CVE-2026-40575"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/40xxx/CVE-2026-40575.json"},{"type":"ADVISORY","url":"https://github.com/oauth2-proxy/oauth2-proxy/security/advisories/GHSA-7x63-xv5r-3p2x"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-40575"},{"type":"REPORT","url":"https://bugzilla.redhat.com/show_bug.cgi?id=2460449"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/oauth2-proxy/oauth2-proxy","events":[{"introduced":"01386bf30348f75590df61a3408187696fef6d4b"},{"fixed":"5961fd99b42c3625b8ef08690d38be5cb37f44b0"}],"database_specific":{"source":["AFFECTED_FIELD","CPE_RANGE"],"cpe":"cpe:2.3:a:oauth2_proxy_project:oauth2_proxy:*:*:*:*:*:*:*:*","extracted_events":[{"introduced":"7.5.0"},{"fixed":"7.15.2"}]}}],"versions":["v7.15.1","v7.15.0","v7.14.3","v7.14.2","v7.14.1","v7.14.0","v7.13.0","v7.12.0","v7.11.0","v7.10.0","v7.9.0","v7.8.2","v7.8.1","v7.8.0","v7.7.1","v7.7.0","v7.6.0","v7.5.1","v7.5.0"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-40575.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N"}]}