A flaw was found in the Apache Log4j logging library 2.x. when the logging configuration uses a non-default Pattern Layout with a Context Lookup. Attackers with control over Thread Context Map (MDC) input data can craft malicious input data that contains a recursive lookup and can cause Denial of Service.

A memory leak flaw was found in Apache Tomcat, where an HTTP upgrade connection does not release for WebSocket connections once the WebSocket connection is closed. If a sufficient number of such requests are made, an OutOfMemoryError occurs, leading to a denial of service. The highest threat from this vulnerability is to system availability.