{"id":"CVE-2026-76835","aliases":["BIT-oauth2-proxy-2026-40575","BIT-oauth2-proxy-2026-76835","EUVD-2026-65061","GHSA-7x63-xv5r-3p2x","GHSA-vvqv-7vrf-88vh","GO-2026-5236","RHSA-2026:74536"],"status":"published","title":"OAuth2 Proxy 7.15.2 through 7.15.4 Authentication Bypass via X-Forwarded-Uri Under the Default Trusted Proxy Set","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.","severity":{"version":"4.0","score":9.3,"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","level":"critical","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-09","score":0.00453,"percentile":0.39591,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":false},"cwes":["CWE-290"],"published":"2026-04-15T19:21:06Z","modified":"2026-10-28T02:31:01Z","affected":[{"source":"osv","ecosystem":"Bitnami","package":"oauth2-proxy","ranges":[{"type":"SEMVER","events":[{"introduced":"7.5.0"},{"fixed":"7.15.2"}]}],"bundled":2},{"source":"osv","ecosystem":"Bitnami","package":"oauth2-proxy","ranges":[{"type":"SEMVER","events":[{"introduced":"7.15.2"},{"fixed":"7.15.5"}]}],"bundled":2},{"source":"osv","ecosystem":"Go","package":"github.com/oauth2-proxy/oauth2-proxy/v7","ranges":[{"type":"SEMVER","events":[{"introduced":"7.5.0"},{"fixed":"7.15.2"}]}],"bundled":2},{"source":"osv","ecosystem":"Go","package":"github.com/oauth2-proxy/oauth2-proxy","ranges":[{"type":"SEMVER","events":[{"introduced":"0"}]}],"bundled":2},{"source":"osv","ecosystem":"Go","package":"github.com/oauth2-proxy/oauth2-proxy/v7","ranges":[{"type":"SEMVER","events":[{"introduced":"7.5.0"},{"fixed":"7.15.2"}]}],"bundled":2},{"source":"osv","ecosystem":"Red Hat:hummingbird:1","package":"oauth2-proxy","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0:7.15.5-0.1.hum1"}]}],"bundled":2}],"products":[{"vendor":"oauth2-proxy","product":"oauth2-proxy"}],"references":[{"url":"https://github.com/oauth2-proxy/oauth2-proxy","tags":["product","web","package","article"]},{"url":"https://github.com/oauth2-proxy/oauth2-proxy/issues/3506","tags":["issue-tracking","exploit","web","report","article"]},{"url":"https://github.com/oauth2-proxy/oauth2-proxy/blob/v7.15.4/pkg/apis/middleware/scope.go","tags":["technical-description","web","article"]},{"url":"https://github.com/oauth2-proxy/oauth2-proxy/security/advisories/GHSA-7x63-xv5r-3p2x","tags":["vendor-advisory","advisory","web","article"]},{"url":"https://www.vulncheck.com/advisories/oauth2-proxy-through-authentication-bypass-via-x-forwarded-uri-under-the-default-trusted-proxy-set","tags":["third-party-advisory","web","advisory","article"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-76835","tags":["web","advisory"]},{"url":"https://github.com/advisories/GHSA-vvqv-7vrf-88vh"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-40575","tags":["web","advisory"]},{"url":"https://access.redhat.com/security/cve/CVE-2026-40575","tags":["web","advisory"]},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2460449","tags":["web","report"]},{"url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-40575.json","tags":["web"]},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/40xxx/CVE-2026-40575.json","tags":["advisory"]},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/76xxx/CVE-2026-76835.json","tags":["advisory"]},{"url":"https://access.redhat.com/errata/RHSA-2026:74536","tags":["advisory"]},{"url":"https://images.redhat.com/","tags":["article"]},{"url":"https://access.redhat.com/security/cve/CVE-2026-76835","tags":["report"]},{"url":"https://access.redhat.com/security/updates/classification/","tags":["article"]},{"url":"https://access.redhat.com/security/cve/CVE-2026-56851","tags":["report"]},{"url":"https://security.access.redhat.com/data/csaf/v2/advisories/2026/rhsa-2026_74536.json","tags":["advisory"]},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2547607","tags":["report"]},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-56851","tags":["advisory"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-56851","tags":["advisory"]},{"url":"https://go.dev/cl/793360","tags":["article"]},{"url":"https://go.dev/issue/80112","tags":["article"]},{"url":"https://pkg.go.dev/vuln/GO-2026-6629","tags":["advisory"]},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2522418","tags":["report"]},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-76835","tags":["advisory"]}],"sources":{"cve":[{"id":"CVE-2026-76835","title":"OAuth2 Proxy 7.15.2 through 7.15.4 Authentication Bypass via X-Forwarded-Uri Under the Default Trusted Proxy Set","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.","status":"published","published":"2026-08-24T17:55:39.829Z","modified":"2026-10-08T15:25:05.218Z","cvss":[{"version":"4.0","score":9.3,"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","level":"critical","assessor":"cna"},{"version":"3.1","score":9.1,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N","level":"critical","assessor":"cna"}],"cwes":["CWE-290"],"updated_at":"2026-11-02T13:46:32.755125Z"}],"euvd":[{"id":"EUVD-2026-65061","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.","status":"published","published":"2026-08-24T17:55:39Z","modified":"2026-10-08T15:25:05Z","cvss":[{"version":"4.0","score":9.3,"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","level":"critical"}],"updated_at":"2026-11-02T17:27:31.218078Z"}],"ghsa":[{"id":"GHSA-vvqv-7vrf-88vh","title":"OAuth2 Proxy honours a client-supplied X-Forwarded-Uri header when deciding whether a request may...","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.","status":"published","published":"2026-08-24T18:31:57Z","modified":"2026-08-24T18:32:04Z","cvss":[{"version":"4.0","score":9.3,"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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","level":"critical"},{"version":"3.1","score":9.1,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N","level":"critical"}],"cwes":["CWE-290"],"updated_at":"2026-11-02T15:10:54.733778Z"}],"nvd":[{"id":"CVE-2026-76835","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.","status":"published","published":"2026-08-24T18:17:21.57Z","modified":"2026-10-13T09:10:00.323Z","cvss":[{"version":"4.0","score":9.3,"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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","level":"critical","assessor":"secondary"},{"version":"3.1","score":9.1,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N","level":"critical","assessor":"secondary"}],"cwes":["CWE-290"],"updated_at":"2026-11-02T14:12:41.018848Z"}],"osv":[{"id":"CVE-2026-40575","title":"OAuth2 Proxy has an Authentication Bypass via X-Forwarded-Uri Header Spoofing","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.","status":"published","published":"2026-04-21T23:20:30.486Z","modified":"2026-10-28T02:30:34.431098752Z","cvss":[{"version":"3.1","score":9.1,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N","level":"critical"}],"cwes":["CWE-290"],"updated_at":"2026-11-02T15:45:03.424067Z"},{"id":"CVE-2026-76835","title":"OAuth2 Proxy 7.15.2 through 7.15.4 Authentication Bypass via X-Forwarded-Uri Under the Default Trusted Proxy Set","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.","status":"published","published":"2026-08-24T17:55:39.829Z","modified":"2026-10-28T02:31:01.309244598Z","cvss":[{"version":"4.0","score":9.3,"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","level":"critical"}],"cwes":["CWE-290"],"updated_at":"2026-11-02T15:45:17.102988Z"},{"id":"GHSA-7x63-xv5r-3p2x","title":"OAuth2 Proxy has an Authentication Bypass via X-Forwarded-Uri Header Spoofing","description":"### Impact\n\nA configuration-dependent authentication bypass exists in OAuth2 Proxy.\n\nDeployments are affected when all of the following are true:\n\n* OAuth2 Proxy is configured with `--reverse-proxy`\n* and at least one rule is defined with `--skip_auth_routes` or the legacy `--skip-auth-regex`\n\nOAuth2 Proxy may trust a client-supplied `X-Forwarded-Uri` header when `--reverse-proxy` is enabled and `--skip-auth-route` or `--skip-auth-regex` 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.\n\nThis can result in an unauthenticated remote attacker bypassing authentication and accessing protected routes without a valid session.\n\n\n### Patches\nThis issue is addressed as part of the newly introduced `--trusted-proxy-ip` flag in `v7.15.2`. If you leave it unset, OAuth2 Proxy will **continue to trust ALL** source IPs (0.0.0.0/0) for backwards compatibility, which means a client may still be able to spoof forwarded headers. Therefore after upgrading we urge you to use the new `--trusted-proxy-ip` flag to set the IPs or CIDR ranges of the reverse proxies that are allowed to send `X-Forwarded-*` headers and furthermore implement the mitigation steps outlined below to properly configure your load balancer infrastructure.\n\n### Mitigation\n\n- Strip any client-provided `X-Forwarded-Uri` header at the reverse proxy or load balancer level\n- Explicitly overwrite `X-Forwarded-Uri` with the actual request URI before forwarding requests to OAuth2 Proxy\n\n  Example nginx mitigation for the auth subrequest:\n  ```\n    location /internal-auth/ {\n      internal; # Ensure external users can't access this path\n  \n      # Make sure the OAuth2 Proxy knows where the original request came from.\n      proxy_set_header Host       $host;\n      proxy_set_header X-Real-IP  $remote_addr;\n      # set the value to the actual $request_uri and therefore strip any user provided X-Forwarded-Uri\n      proxy_set_header X-Forwarded-Uri $request_uri;\n  \n      proxy_pass http://oauth2-proxy:4180/;\n    }\n  ```\n- Restrict direct client access to OAuth2 Proxy so it can only be reached through a trusted reverse proxy\n- Remove or narrow `--skip-auth-route` / `--skip-auth-regex` rules where possible","status":"published","published":"2026-04-15T19:21:06Z","modified":"2026-09-25T14:25:56.584542414Z","cvss":[{"version":"3.1","score":9.1,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N","level":"critical"}],"cwes":["CWE-290"],"updated_at":"2026-11-02T15:46:41.732368Z"},{"id":"RHSA-2026:74536","title":"Red Hat Security Advisory: Red Hat Hardened Images RPMs bug fix and enhancement update","status":"published","published":"2026-10-02T10:25:59Z","modified":"2026-10-20T10:43:37.08622866Z","cvss":[{"version":"3.1","score":9.1,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N","level":"critical"}],"updated_at":"2026-11-02T15:53:22.928316Z"},{"id":"BIT-oauth2-proxy-2026-40575","title":"OAuth2 Proxy has an Authentication Bypass via X-Forwarded-Uri Header Spoofing","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.","status":"published","published":"2026-04-23T08:47:02.681Z","modified":"2026-09-25T14:25:56.584542414Z","updated_at":"2026-11-02T15:28:34.343258Z"},{"id":"BIT-oauth2-proxy-2026-76835","title":"OAuth2 Proxy 7.15.2 through 7.15.4 Authentication Bypass via X-Forwarded-Uri Under the Default Trusted Proxy Set","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.","status":"published","published":"2026-09-25T12:27:39.116Z","modified":"2026-10-01T12:15:02.476980667Z","updated_at":"2026-11-02T15:28:34.343258Z"},{"id":"GO-2026-5236","title":"OAuth2 Proxy has an Authentication Bypass via X-Forwarded-Uri Header Spoofing in github.com/oauth2-proxy/oauth2-proxy","description":"OAuth2 Proxy has an Authentication Bypass via X-Forwarded-Uri Header Spoofing in github.com/oauth2-proxy/oauth2-proxy","status":"published","published":"2026-06-25T18:43:15Z","modified":"2026-09-25T14:25:56.584542414Z","updated_at":"2026-11-02T15:47:02.556545Z"}]}}