CVE-2021-42340: Apache Tomcat: DoS via memory leak with WebSocket connections

[Mark Thomas <markt () apache org>]

The fix for bug 63362 present in Apache Tomcat 10.1.0-M1 to 10.1.0-M5, 
10.0.0-M1 to 10.0.11, 9.0.40 to 9.0.53 and 8.5.60 to 8.5.71 introduced a 
memory leak. The object introduced to collect metrics for HTTP upgrade 
connections was not released for WebSocket connections once the 
connection was closed. This created a memory leak that, over time, could 
lead to a denial of service via an OutOfMemoryError.

References:

https://lists.apache.org/thread.html/r83a35be60f06aca2065f188ee542b9099695d57ced2e70e0885f905c%40%3Cannounce.tomcat.apache.org%3E