CVE-2026-76835
published 2026-08-24CVE-2026-76835: OAuth2 Proxy honours a client-supplied X-Forwarded-Uri header when deciding whether a request may skip authentication, because the guard added for…
PriorityP261critical9.1CVSS 3.1
AVNACLPRNUINSUCHIHAN
EPSS
0.45%
36.9th percentile
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.
Affected
2 ranges
| Vendor | Product | Version range | Fixed in |
|---|---|---|---|
| devspaces | oauth2-proxy-rhel9 | — | — |
| oauth2-proxy | oauth2-proxy | — | — |
CVSS provenance
nvdv3.19.1CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
nvdv4.09.3CRITICALCVSS: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
vendor_redhat9.1CRITICAL
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GHSA
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
ghsa_unreviewed·2026-08-24·CVSS 9.1
CVE-2026-76835 [CRITICAL] CWE-290 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
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 therefor
Red Hat
github.com/oauth2-proxy/oauth2-proxy: OAuth2 Proxy 7.15.2 through 7.15.4 Authentication Bypass via X-Forwarded-Uri Under the Default Trusted Proxy Set
vendor_redhat·2026-08-24·CVSS 9.1
CVE-2026-76835 [CRITICAL] CWE-290 github.com/oauth2-proxy/oauth2-proxy: OAuth2 Proxy 7.15.2 through 7.15.4 Authentication Bypass via X-Forwarded-Uri Under the Default Trusted Proxy Set
github.com/oauth2-proxy/oauth2-proxy: OAuth2 Proxy 7.15.2 through 7.15.4 Authentication Bypass via X-Forwarded-Uri Under the Default Trusted Proxy Set
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 d
No detection rules found.
No public exploits indexed.
https://github.com/oauth2-proxy/oauth2-proxyhttps://github.com/oauth2-proxy/oauth2-proxy/blob/v7.15.4/pkg/apis/middleware/scope.gohttps://github.com/oauth2-proxy/oauth2-proxy/issues/3506https://github.com/oauth2-proxy/oauth2-proxy/security/advisories/GHSA-7x63-xv5r-3p2xhttps://www.vulncheck.com/advisories/oauth2-proxy-through-authentication-bypass-via-x-forwarded-uri-under-the-default-trusted-proxy-sethttps://github.com/oauth2-proxy/oauth2-proxy/issues/3506
2026-08-24
Published