Auth bypass in GNU Mailman
CVE-2025-43921
GNU Mailman 2.1.39, as bundled in cPanel (and WHM), allows unauthenticated attackers to create lists via the /mailman/create endpoint. NOTE: multiple third parties report that they are unable to reproduce this, regardless of whether cPanel or WHM is used.
Vulnerability class: Broken Access Control
Published · last modified .
CVSS v3 metric
CVSS v3 base score 5.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N.
EPSS exploit prediction
EPSS: 0.005 (36.7th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 37th percentile — 36.7% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.004 · newest: 0.005 · 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-2025-43921 (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-2025-43921?
- CVE-2025-43921 is a medium-severity vulnerability in GNU Mailman, classified under Incorrect Authorization. CVSS score: 5.3/10. Published 2025-04-20.
- How severe is CVE-2025-43921?
- Medium severity. CVSS v3 base score is 5.3 out of 10.
- Is CVE-2025-43921 known to be exploited?
- 4 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.