The MITRE CVE dictionary describes this issue as:
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.
Find out more about CVE-2018-1303 from the
MITRE CVE dictionary dictionary and
The versions of httpd package shipped with Red Hat Enterprise Linux are by default configured in prefork MPM mode, which means that this flaw can result in a crash of child process. The main web server process will not be killed. Also, though the module is loaded by default, it needs to be specifically enabled in order to be exposed to the security flaw.