CVE-2025-43920: GNU Mailman

High severity, CVSS 8.1. EPSS: 0.6% chance of exploitation in the next 30 days.

GNU Mailman 2.1.39, as bundled in cPanel (and WHM), in certain external archiver configurations, allows unauthenticated attackers to execute arbitrary OS commands via shell metacharacters in an email Subject line. NOTE: multiple third parties report that they are unable to reproduce this, regardless of whether cPanel or WHM is used.

Affected products

• GNU Mailman: from 2.1.1, up to and including 2.1.39

Published 2025-04-20. Last modified 2026-06-17.