CVE-2025-43920 Command injection in Mailman

Medium 5.4 Published 20 Apr 2025 Updated 28 Apr 2025

Unauthenticated attackers can execute arbitrary OS commands via email subject lines in specific external archiver configurations of GNU Mailman.

Exploited in the wild: Not known
Login needed: Not needed
Attackable: Over the internet
Victim action needed: Not needed
Fix: None listed

What is CVE-2025-43920?

CVE-2025-43920 is a medium-severity command injection vulnerability in GNU Mailman, published on 20 Apr 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

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.

Weakness: CWE-78

Which versions are affected by CVE-2025-43920?

It affects 1 product.

Products include Gnu Mailman.

How do I fix CVE-2025-43920?

No fix has been published for CVE-2025-43920 yet. Limit exposure of the affected software until one is available.

Upgrade, and pass arguments to programs as a list instead of through a shell. More about Command injection.

Is CVE-2025-43920 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2025-43920 exists.

Public exploit code: 1 proofs of concept on GitHub.

Sources

Also known as GHSA-35m2-m3ch-fgh4.