{"cve":"CVE-2026-76835","nvd":{"published":"2026-08-24T18:17:21.570","modified":"2026-10-13T09:10:00.323","status":"Deferred","description":"OAuth2 Proxy honours a client-supplied X-Forwarded-Uri header when deciding whether a request may skip authentication, because the guard added for CVE-2026-40575 is inert in the default reverse-proxy configuration. GetRequestURI in pkg/requests/util/util.go prefers that header over the real request URI whenever CanTrustForwardedHeaders returns true, and isAllowedPath in oauthproxy.go matches the skip_auth_routes and skip_auth_regex allow list against the resulting path. CanTrustForwardedHeaders in pkg/apis/middleware/scope.go grants that trust when the caller's address is in the trusted proxy set, and buildTrustedProxyNetSet falls back to defaultTrustedProxyIPs, which is 0.0.0.0/0 and ::/0, whenever reverse proxy mode is enabled without trusted_proxy_ip configured. Every client is therefore treated as a trusted proxy. An unauthenticated attacker can request a protected upstream path while setting X-Forwarded-Uri to a value matching an allow-listed route, so the skip-auth decision is made against the spoofed value while the upstream receives the protected path unchanged.","cvss_v4":{"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N","score":9.3},"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N","score":9.1},"cwes":["CWE-290"],"references":["https://github.com/oauth2-proxy/oauth2-proxy","https://github.com/oauth2-proxy/oauth2-proxy/blob/v7.15.4/pkg/apis/middleware/scope.go","https://github.com/oauth2-proxy/oauth2-proxy/issues/3506","https://github.com/oauth2-proxy/oauth2-proxy/security/advisories/GHSA-7x63-xv5r-3p2x","https://www.vulncheck.com/advisories/oauth2-proxy-through-authentication-bypass-via-x-forwarded-uri-under-the-default-trusted-proxy-set"],"products":[],"source":"nvd","synced_at":"2026-10-19T22:50:17.453294893+00:00"},"epss":{"cve":"CVE-2026-76835","score":0.00453,"percentile":0.39066,"date":"2026-10-25"},"kev":null,"osv":[{"id":"GHSA-7x63-xv5r-3p2x","url":"https://osv.dev/vulnerability/GHSA-7x63-xv5r-3p2x","summary":"OAuth2 Proxy has an Authentication Bypass via X-Forwarded-Uri Header Spoofing","modified":"2026-09-25T14:25:56.584542414Z","packages":[{"ecosystem":"Go","name":"github.com/oauth2-proxy/oauth2-proxy/v7","purl":"pkg:golang/github.com/oauth2-proxy/oauth2-proxy/v7","ranges":[">=7.5.0 <7.15.2"],"fixed":["7.15.2"]}]},{"id":"GO-2026-5236","url":"https://osv.dev/vulnerability/GO-2026-5236","summary":"OAuth2 Proxy has an Authentication Bypass via X-Forwarded-Uri Header Spoofing in github.com/oauth2-proxy/oauth2-proxy","modified":"2026-09-25T14:25:56.584542414Z","packages":[{"ecosystem":"Go","name":"github.com/oauth2-proxy/oauth2-proxy","purl":"pkg:golang/github.com/oauth2-proxy/oauth2-proxy","ranges":["all versions"],"fixed":[]},{"ecosystem":"Go","name":"github.com/oauth2-proxy/oauth2-proxy/v7","purl":"pkg:golang/github.com/oauth2-proxy/oauth2-proxy/v7","ranges":[">=7.5.0 <7.15.2"],"fixed":["7.15.2"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}