The following information has been provided by the HTTPD announce mailing list.
CVE-2017-9789: Read after free in mod_http2.c
Vendor: The Apache Software Foundation
When under stress, closing many connections, the HTTP/2
handling code would sometimes access memory after it has
been freed, resulting in potentially erratic behaviour.
2.4.26 users of mod_http2 should upgrade to 2.4.27.
The Apache HTTP Server security team would like to thank Robert Święcki
for reporting this issue.