Fixed in Apache Tomcat 9.0.38

Moderate: HTTP/2 request mix-up CVE-2020-13943

If an HTTP/2 client exceeded the agreed maximum number of concurrent streams for a connection (in violation of the HTTP/2 protocol), it was possible that a subsequent request made on that connection could contain HTTP headers - including HTTP/2 pseudo headers - from a previous request rather than the intended headers. This could lead to users seeing responses for unexpected resources.

This was fixed with commit 55911430.

This issue was identified by the Apache Tomcat Security team on 23 July 2020. The issue was made public on 12 October 2020.

Affects: 9.0.0.M1 to 9.0.37