User Impersonation Affecting github.com/oauth2-proxy/oauth2-proxy/pkg/validation package, versions <7.15.2
Threat Intelligence
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Test your applications- Snyk IDSNYK-GOLANG-GITHUBCOMOAUTH2PROXYOAUTH2PROXYPKGVALIDATION-16121349
- published22 Apr 2026
- disclosed22 Apr 2026
- creditRahul Maini
Introduced: 22 Apr 2026
CVE-2026-40575 Â (opens in a new tab)How to fix?
Upgrade github.com/oauth2-proxy/oauth2-proxy/pkg/validation to version 7.15.2 or higher.
Overview
Affected versions of this package are vulnerable to User Impersonation via the X-Forwarded-Uri header when the --reverse-proxy setting is enabled and either --skip-auth-regex or --skip-auth-route is configured. An attacker can gain unauthorized access to protected routes by spoofing the X-Forwarded-Uri header, causing authentication and skip-auth rules to be evaluated against a different path than the one actually requested.
Workaround
This vulnerability can be mitigated by stripping any client-provided X-Forwarded-Uri header at the reverse proxy or load balancer level, explicitly overwriting X-Forwarded-Uri with the actual request URI before forwarding requests, restricting direct client access so only a trusted reverse proxy can reach the service, and/or removing or narrowing --skip-auth-regex / --skip-auth-route rules. For nginx-based deployments, ensure X-Forwarded-Uri is set by nginx and not passed through from the client.