A regression in the fix for bug 66512 in Apache Tomcat 11.0.0-M5, 10.1.8, 9.0.74 and 8.5.88 meant that, if a response did not include any HTTP headers no AJP SEND_HEADERS messare woudl be sent for the response which in turn meant that at least one AJP proxy (mod_proxy_ajp) would use the response headers from the previous request leading to an information leak.

If an HTTP/2 client connecting to Apache Tomcat 10.0.0-M1 to 10.0.0-M7, 9.0.0.M1 to 9.0.37 or 8.5.0 to 8.5.57 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.