CVE-2016-4556: Canonical Ubuntu Linux

High severity, CVSS 7.5. EPSS: 23.1% chance of exploitation in the next 30 days.

Double free vulnerability in Esi.cc in Squid 3.x before 3.5.18 and 4.x before 4.0.10 allows remote servers to cause a denial of service (crash) via a crafted Edge Side Includes (ESI) response.

Affected products

• Canonical Ubuntu Linux: version 12.04 only; version 14.04 only; version 15.10 only; version 16.04 only
• Oracle Linux: version 6 only; version 7 only
• Squid-Cache Squid: version 3.0 only; version 3.1 only; version 3.1.0.1 only; version 3.1.0.2 only; version 3.1.0.3 only; version 3.1.0.4 only; …

Published 2016-05-10. Last modified 2026-06-17.