CVE-2026-40574: oauth2_proxy_project oauth2_proxy Incorrect Authorization

Vulnerability summary

CVE-2026-40574 is a medium (CVSS 6.8) Incorrect Authorization vulnerability in oauth2_proxy_project oauth2_proxy. EPSS estimates a 0.34% chance of exploitation in the next 30 days, higher than 25.7% of scored vulnerabilities.

Timeline

1. 21-04-2026
   PublishedVulnerability first disclosed.
2. 21-04-2026
   Last modifiedVulnerability information updated.

Description

OAuth2 Proxy is a reverse proxy that provides authentication using OAuth2 providers. Prior to 7.15.2, an authorization bypass exists in OAuth2 Proxy as part of the email_domain enforcement option. An attacker may be able to authenticate with an email claim such as attacker@evil.com@company.com and satisfy an allowed domain check for company.com, even though the claim is not a valid email address. The issue ONLY affects deployments that rely on email_domain restrictions and accept email claim values from identity providers or claim mappings that do not strictly enforce normal email syntax. This vulnerability is fixed in 7.15.2.

• CWE-863Incorrect AuthorizationThe product performs an authorization check when an actor attempts to access a resource or perform an action, but it does not correctly perform the check.