srl
OAuth Attacks
OAuth is a standard designed to enable secure authorization between services and applications. It is widely used in Single Sign-On (SSO) scenarios, where a user can authenticate once and access multiple applications without sharing their credentials with each service.
2025–2026 context: OAuth 2.0/2.1 is now the backbone of almost every authentication system, and the vulnerability classes have moved out of the redirect_uri parameter and into the libraries that implement the flows. The current CVE feed is dominated by state-parameter persistence failures (Authlib, fastapi-sso), PKCE downgrade bypasses (Cloudflare workers-oauth-provider), OAuth email-linking account takeover (Pingvin Share, AshAuthentication), unauthenticated callback fallback (Feathers, CVSS 9.8), and dynamic client registration that accepts arbitrary redirect URIs.