CVE-2025-43921: mailman Auth Bypass — Exploit

Description

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.

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CVSS v3.1 Score

5.3

MEDIUM

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

Weakness Type (CWE)

CWE-863 Incorrect Authorization

Affected Products

Vendor	Product	Versions
gnu	mailman	2.1.1 — 2.1.39

References

Exploits

https://github.com/0NYX-MY7H/CVE-2025-43921

Other References

https://code.launchpad.net/~mailman-coders/mailman/2.1 https://github.com/cpanel/mailman2-python3 https://www.openwall.com/lists/oss-security/2025/04/21/6

Frequently Asked Questions

What is 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. It has a CVSS v3.1 base score of 5.3 (MEDIUM).

How severe is CVE-2025-43921? +

CVE-2025-43921 has a CVSS v3.1 score of 5.3 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance.

What products are affected by CVE-2025-43921? +

CVE-2025-43921 affects products from gnu, specifically: mailman. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2025-43921? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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CVE-2025-43921