Squid is a caching proxy for the Web supporting HTTP, HTTPS, FTP, and more. It reduces bandwidth and improves response times by caching and reusing frequently-requested web page.

Buffer overflow in Squid allows remote attackers to execute arbitrary code via crafted Edge Side Includes (ESI) responses.(CVE-2016-4054)

ESI is a small markup language for edge level dynamic web content assembly.A stack-based buffer overflow vulnerability exists in the Squid server. The vulnerability is due to an implementation error when the Squid server processes the ESI markup tags.

The vulnerable function is ESIContext::start() . Patch fixes the overflow by checking the size of buffer before copying.

Dell SonicWALL Threat Research Team has researched this vulnerability and released following signature to protect their customers

• IPS 4902:Server Application Shellcode Exploit 20