oauth2-proxy OAuth2 Proxy up to 7.15.4 Reverse-Proxy util.go GetRequestURI X-Forwarded-Uri access control

Summaryinfo

A vulnerability marked as critical has been reported in oauth2-proxy OAuth2 Proxy up to 7.15.4. This issue affects the function GetRequestURI of the file pkg/requests/util/util.go of the component Reverse-Proxy. This manipulation of the argument X-Forwarded-Uri causes access control. This vulnerability appears as CVE-2026-76835. The attack may be initiated remotely. There is no available exploit.

Detailsinfo

A vulnerability was found in oauth2-proxy OAuth2 Proxy up to 7.15.4. It has been declared as critical. Affected by this vulnerability is the function GetRequestURI of the file pkg/requests/util/util.go of the component Reverse-Proxy. The manipulation of the argument X-Forwarded-Uri with an unknown input leads to a access control vulnerability. The CWE definition for the vulnerability is CWE-284. The product does not restrict or incorrectly restricts access to a resource from an unauthorized actor. As an impact it is known to affect confidentiality, integrity, and availability. The summary by CVE is:

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.

It is possible to read the advisory at github.com. This vulnerability is known as CVE-2026-76835 since 08/19/2026. The exploitation appears to be easy. The attack can be launched remotely. The exploitation doesn't need any form of authentication. Technical details of the vulnerability are known, but there is no available exploit. The pricing for an exploit might be around USD $0-$5k at the moment (estimation calculated on 08/24/2026). The attack technique deployed by this issue is T1068 according to MITRE ATT&CK.

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

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Productinfo

Type

• Firewall Software

Vendor

• oauth2-proxy

Name

• OAuth2 Proxy

Version

• 7.15.0
• 7.15.1
• 7.15.2
• 7.15.3
• 7.15.4

CPE 2.3info

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CPE 2.2info

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