X-Forwarded-Uri

Critical Authentication Bypass Vulnerability Found in OAuth2 Proxy, No Patch Released

A severe authentication bypass vulnerability has been identified in the OAuth2 Proxy authentication proxy, tracked as CVE-2026-76835. The issue allows attackers to circumvent authentication by sending crafted X-Forwarded-Uri headers when the trusted_proxy_ip setting is not configured. This affects default reverse proxy configurations and enables unauthorized access to protected paths. Although version 7.15.2 addressed a related flaw under CVE-2026-40575, the vulnerability persists in standard reverse proxy setups. VulnCheck rated the flaw with a CVSS v4.0 base score of 9.3, classifying it as Critical. No patched release is currently available despite ongoing work in the source repository.