CVE-2020-11945: Canonical Ubuntu Linux

Critical severity, CVSS 9.8. EPSS: 27.2% chance of exploitation in the next 30 days.

An issue was discovered in Squid before 5.0.2. A remote attacker can replay a sniffed Digest Authentication nonce to gain access to resources that are otherwise forbidden. This occurs because the attacker can overflow the nonce reference counter (a short integer). Remote code execution may occur if the pooled token credentials are freed (instead of replayed as valid credentials).

Affected products

• Canonical Ubuntu Linux: version 16.04 only; version 18.04 only; version 19.10 only; version 20.04 only
• Debian Debian Linux: version 9.0 only; version 10.0 only
• Fedoraproject Fedora: version 30 only; version 31 only; version 32 only
• Opensuse Leap: version 15.1 only
• Squid-Cache Squid: from 3.0, up to and including 3.5.28; from 4.0, before 4.11 (fixed in 4.11); from 5.0, before 5.0.2 (fixed in 5.0.2)

Published 2020-04-23. Last modified 2026-06-17.