CVE-2021-44143: Debian Linux

Critical severity, CVSS 9.8. EPSS: 3.8% chance of exploitation in the next 30 days.

A flaw was found in mbsync in isync 1.4.0 through 1.4.3. Due to an unchecked condition, a malicious or compromised IMAP server could use a crafted mail message that lacks headers (i.e., one that starts with an empty line) to provoke a heap overflow, which could conceivably be exploited for remote code execution.

Affected products

• Debian Debian Linux: version 9.0 only; version 10.0 only; version 11.0 only
• Fedoraproject Fedora: version 34 only; version 35 only
• Isync Project Isync: from 1.4.0, up to and including 1.4.3

Published 2021-11-22. Last modified 2026-06-17.