Authentication Bypass in OAuth2 Proxy Vulnerability Disclosed
Article Content
- •CVE-2026-76835 allows unauthenticated access via X-Forwarded-Uri manipulation.
- •The vulnerability affects OAuth2 Proxy versions 7.15.2 to 7.15.4 with a CVSS score of 9.1.
- •Operators must configure the --trusted-proxy-ip flag to mitigate the risk.
A vulnerability, CVE-2026-76835, has been identified in OAuth2 Proxy versions 7.15.2 to 7.15.4, allowing unauthenticated remote attackers to bypass authentication by manipulating the X-Forwarded-Uri header. The flaw, with a CVSS score of 9.1, arises when the --reverse-proxy is enabled and specific skip-auth rules are configured. This vulnerability is a continuation of CVE-2026-40575, which was patched in version 7.15.2, but the fix was ineffective due to default settings that trust all IP addresses. The patch for CVE-2026-76835 was released on October 1, 2026, in version 7.15.5, which tightened path matching and improved header resolution. As of now, there is no confirmed exploitation in the wild, and the vulnerability is not listed in the CISA Known Exploited Vulnerabilities catalog. Operators are advised to configure the --trusted-proxy-ip flag and implement additional mitigation measures. The vulnerability primarily affects deployments using Kubernetes ingress architectures and multi-tenant SaaS backends.
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