The remote Debian host is missing a security-related update.
Several security issues have been discovered in the Squid caching proxy. - CVE-2016-4051 : CESG and Yuriy M. Kaminskiy discovered that Squid cachemgr.cgi was vulnerable to a buffer overflow when processing remotely supplied inputs relayed through Squid. - CVE-2016-4052 : CESG discovered that a buffer overflow made Squid vulnerable to a Denial of Service (DoS) attack when processing ESI responses. - CVE-2016-4053 : CESG found that Squid was vulnerable to public information disclosure of the server stack layout when processing ESI responses. - CVE-2016-4054 : CESG discovered that Squid was vulnerable to remote code execution when processing ESI responses. - CVE-2016-4554 : Jianjun Chen found that Squid was vulnerable to a header smuggling attack that could lead to cache poisoning and to bypass of same-origin security policy in Squid and some client browsers. - CVE-2016-4555, CVE-2016-4556 : 'bfek-18' and '@vftable' found that Squid was vulnerable to a Denial of Service (DoS) attack when processing ESI responses, due to incorrect pointer handling and reference counting.
Upgrade the squid3 packages. For the stable distribution (jessie), these problems have been fixed in version 3.4.8-6+deb8u3.