CVE-2025-43920

GNU Mailman 2.1.39, as bundled in cPanel (and WHM), allows unauthenticated attackers to execute...

5.4 MediumPublic exploitDisputed

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.

Attack profile

How easy it is to exploit

Attack vector: Network
Complexity: High
Privileges needed: None
User interaction: None

What an attacker can affect

Confidentiality: Low
Integrity: Low
Availability: None

Exploit likelihood

0.60%Up 0.6 points since Apr 20, 2025

What each source reports

CVE List Score used 5.4

Record: CVE-2025-43920
CVSS 3.1: 5.4 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:L/A:N
Weakness: CWE-78
Updated: 2026-11-02

EUVDEUVD-2025-12591 5.4

Record: EUVD-2025-12591
CVSS 3.1: 5.4 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:L/A:N
Updated: 2026-11-02

GitHub AdvisoriesGHSA-35m2-m3ch-fgh4 5.4

GNU Mailman 2.1.39, as bundled in cPanel (and WHM), allows unauthenticated attackers to execute...

GNU Mailman 2.1.39, as bundled in cPanel (and WHM), allows unauthenticated attackers to execute arbitrary OS commands via shell metacharacters in an email Subject line.

Record: GHSA-35m2-m3ch-fgh4
CVSS 3.1: 5.4 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:L/A:N
Weakness: CWE-78
Updated: 2026-11-02

NVD 5.4

Record: CVE-2025-43920
CVSS 3.1: 5.4 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:L/A:N
CVSS 3.1: 8.1 HighCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
Weakness: CWE-78
Updated: 2026-11-02

OSVUBUNTU-CVE-2025-43920 5.4

Record: UBUNTU-CVE-2025-43920
CVSS 3.1: 5.4 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:L/A:N
CVSS 3.1: 8.1 HighCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
Updated: 2026-11-02

Affected products

gnu mailman

Public exploits

Links only. Every CVE stores no exploit code.

Public exploits
Source	Link	Date
PoC in GitHub	0NYX-MY7H/CVE-2025-43920	2025-04-20

History

History
Recorded	Changed	Sources
Nov 3, 2026	affected
Nov 2, 2026	first indexed	CVE List, EUVD, GitHub Advisories, NVD, OSV, PoC in GitHub

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2025-43920 is a medium vulnerability (CVSS 5.4) in Gnu Mailman, published April 20, 2025. Its validity is disputed. Public exploit code exists. EPSS puts the chance of exploitation in the next 30 days at 0.60%, the 48th percentile.