CVE-2016-4554: Canonical Ubuntu Linux

High severity, CVSS 8.6. EPSS: 38.9% chance of exploitation in the next 30 days.

mime_header.cc in Squid before 3.5.18 allows remote attackers to bypass intended same-origin restrictions and possibly conduct cache-poisoning attacks via a crafted HTTP Host header, aka a "header smuggling" issue.

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: up to and including 3.5.17

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