What is CVE-2021-43331?

CVE-2021-43331 is a medium-severity vulnerability in GNU Mailman, classified under Cross-site Scripting. CVSS score: 6.1/10. Published 2021-11-12.

How severe is CVE-2021-43331?

Medium severity. CVSS v3 base score is 6.1 out of 10.

Is CVE-2021-43331 known to be exploited?

1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.

XSS in GNU Mailman

CVE-2021-43331

In GNU Mailman before 2.1.36, a crafted URL to the Cgi/options.py user options page can execute arbitrary JavaScript for XSS.

Vulnerability class: XSS (Cross-Site Scripting)

Published 2021-11-12 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 6.1 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N.

EPSS exploit prediction

EPSS: 0.014 (71.0th percentile), scored 2026-09-29.

Low probability of exploitation in the next 30 days, but still tracked. 71st percentile — 71.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.013 · newest: 0.014 · change: +0.001

Affected products

GNU Mailman
Debian Linux — versions 9.0

Weakness classification (CWE)

CWE-79 — Cross-site Scripting

Public proof-of-concept exploits

ARPSyndicate/cvemon

References

bugs.launchpad.net/mailman/+bug/1949401 (Patch, Third Party Advisory, Issue Tracking)
mail.python.org/archives/list/mailman-announce@python.org/message/I2X7PSFXIEPLM…
lists.debian.org/debian-lts-announce/2022/06/msg00011.html (mailing-list, Mailing List, Third Party Advisory)

Frequently asked questions

What is CVE-2021-43331?: CVE-2021-43331 is a medium-severity vulnerability in GNU Mailman, classified under Cross-site Scripting. CVSS score: 6.1/10. Published 2021-11-12.
How severe is CVE-2021-43331?: Medium severity. CVSS v3 base score is 6.1 out of 10.
Is CVE-2021-43331 known to be exploited?: 1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.