CVE-2016-4553: Canonical Ubuntu Linux

High severity, CVSS 8.6. EPSS: 80% chance of exploitation in the next 30 days.

client_side.cc in Squid before 3.5.18 and 4.x before 4.0.10 does not properly ignore the Host header when absolute-URI is provided, which allows remote attackers to conduct cache-poisoning attacks via an HTTP request.

Affected products

• Canonical Ubuntu Linux: version 12.04 only; version 14.04 only; version 15.10 only; version 16.04 only
• Oracle Linux: version 7 only
• Squid-Cache Squid: up to and including 3.5.17; version 4.0.1 only; version 4.0.2 only; version 4.0.3 only; version 4.0.4 only; version 4.0.5 only; …

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