Preface: Regular Expressions are efficient in that one line of code can save you writing hundreds of lines. But they’re normally slower (even pre-compiled) than thoughtful hand written code simply due to the overhead. Generally the simpler the objective the worse Regular Expressions are. They’re better for complex operations.
Background: OAuth2 Proxy is used to add authentication to applications that don’t natively support it, acting as a reverse proxy that handles authentication using OAuth2 providers like Google, GitHub, or Okta. It simplifies the process of adding authentication to existing applications by separating the authentication logic from the application code. This allows developers to focus on building their core application logic without needing to implement complex authentication workflows.
Vulnerability details: In versions 7.10.0 and below, oauth2-proxy deployments are vulnerable when using the skip_auth_routes configuration option with regex patterns. Attackers can bypass authentication by crafting URLs with query parameters that satisfy configured regex patterns, allowing unauthorized access to protected resources. The issue stems from skip_auth_routes matching against the full request URI. Deployments using skip_auth_routes with regex patterns containing wildcards or broad matching patterns are most at risk.
Resolution: This issue is fixed in version 7.11.0
Workarounds include: auditing all skip_auth_routes configurations for overly permissive patterns, replacing wildcard patterns with exact path matches where possible, ensuring regex patterns are properly anchored (starting with ^ and ending with $), or implementing custom validation that strips query parameters before regex matching.
Official announcement: Please see the link for details https://nvd.nist.gov/vuln/detail/CVE-2025-54576
