A specially crafted HTTP request header could have crashed the Apache HTTP Server prior to version 2.4.30 due to an out of bound read while preparing data to be cached in shared memory. It could be used as a Denial of Service attack against users of mod_cache_socache. The vulnerability is considered as low risk since mod_cache_socache is not widely used, mod_cache_disk is not concerned by this vulnerability.
https://www.tenable.com/security/tns-2019-09
https://www.debian.org/security/2018/dsa-4164
https://usn.ubuntu.com/3627-2/
https://usn.ubuntu.com/3627-1/
https://support.hpe.com/hpsc/doc/public/display?docLocale=en_US&docId=emr_na-hpesbux03909en_us
https://security.netapp.com/advisory/ntap-20180601-0004/
https://httpd.apache.org/security/vulnerabilities_24.html
https://access.redhat.com/errata/RHSA-2019:0367
https://access.redhat.com/errata/RHSA-2019:0366
https://access.redhat.com/errata/RHSA-2018:3558
http://www.securitytracker.com/id/1040572