RCE in GNU Mailman
CVE-2025-43920
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.
Vulnerability class: Command Injection (OS Command Injection)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 5.4 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:L/A:N.
EPSS exploit prediction
EPSS: 0.006 (45.9th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 46th percentile — 45.9% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.006 · newest: 0.006 · change: +0.000
Affected products
- GNU Mailman — versions 2.1.39
Weakness classification (CWE)
Public proof-of-concept exploits
References
- code.launchpad.net/~mailman-coders/mailman/2.1 (Product)
- github.com/0NYX-MY7H/CVE-2025-43920 (Exploit, Third Party Advisory)
- github.com/cpanel/mailman2-python3
- www.openwall.com/lists/oss-security/2025/04/21/6
Frequently asked questions
- What is CVE-2025-43920?
- CVE-2025-43920 is a medium-severity vulnerability in GNU Mailman, classified under OS Command Injection. CVSS score: 5.4/10. Published 2025-04-20.
- How severe is CVE-2025-43920?
- Medium severity. CVSS v3 base score is 5.4 out of 10.
- Is CVE-2025-43920 known to be exploited?
- 4 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.