CVE-2018-1000024

The Squid Software Foundation Squid HTTP Caching Proxy version 3.0 to 3.5.27, 4.0 to 4.0.22 contains a Incorrect Pointer Handling vulnerability in ESI Response Processing that can result in Denial of Service for all clients using the proxy… This attack appear to be exploitable via Remote server delivers an HTTP response payload containing valid but unusual ESI syntax… This vulnerability appears to have been fixed in 4.0.23 and later.

Mitigation

A workaround for this issue is to not use the internal ESI parser, which can be achieved by adding either the "esi_parser expat" or "esi_parser libxml2" configuration directive to the squid configuration file (for example /etc/squid/squid.conf).