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EUVD-2026-337271

fkie_cve-2026-40575

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.

GHSA-7x63-xv5r-3p2x — OAuth2 Proxy has an Authentication Bypass via X-Forwarded-Uri Header Spoofing

Affected: Go: github.com/oauth2-proxy/oauth2-proxy/v7

### Impact

A configuration-dependent authentication bypass exists in OAuth2 Proxy.

Deployments are affected when all of the following are true:

* OAuth2 Proxy is configured with `--reverse-proxy` * and at least one rule is defined with `--skip_auth_routes` or the legacy `--skip-auth-regex`

OAuth2 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.

This can result in an unauthenticated remote attacker bypassing authentication and accessing protected routes without a valid session.

### Patches This 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.

### Mitigation

- Strip any client-provided `X-Forwarded-Uri` header at the reverse proxy or load balancer level - Explicitly overwri…

RHSA-2026:58471 — Red Hat Security Advisory: Red Hat Hardened Images RPMs bug fix and enhancement update

oauth2-proxy: github.com/oauth2-proxy/oauth2-proxy: OAuth2 Proxy: Authentication bypass due to spoofed X-Forwarded-Uri header