In spring security versions prior to 5.4.11+, 5.5.7+ , 5.6.4+ and older unsupported versions, RegexRequestMatcher can easily be misconfigured to be bypassed on some servlet containers. Applications using RegexRequestMatcher with `.` in the regular expression are possibly vulnerable to an authorization bypass.

Spring Security versions 5.5.x prior to 5.5.1, 5.4.x prior to 5.4.7, 5.3.x prior to 5.3.10 and 5.2.x prior to 5.2.11 are susceptible to a Denial-of-Service (DoS) attack via the initiation of the Authorization Request in an OAuth 2.0 Client Web and WebFlux application. A malicious user or attacker can send multiple requests initiating the Authorization Request for the Authorization Code Grant, which has the potential of exhausting system resources using a single session or multiple sessions.