CVE-2021-40347

Name: CVE-2021-40347
Creator: NVD / NIST
Published: 2021-09-10T19:15:08.163+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

MEDIUMCVSS 5.4/10EPSS 1.09%

Last modified Jun 17, 2026

CVE-2021-40347 is a medium-severity vulnerability rated 5.4/10 on the CVSS scale. An issue was discovered in views/list.py in GNU Mailman Postorius before 1.3.5. An attacker (logged into any account) can send a crafted POST request to unsubscribe any user from a mailing list, also revealing whether that address was subscribed in the first place.. EPSS estimates a 1.09% chance of exploitation in the next 30 days.

Description

An issue was discovered in views/list.py in GNU Mailman Postorius before 1.3.5. An attacker (logged into any account) can send a crafted POST request to unsubscribe any user from a mailing list, also revealing whether that address was subscribed in the first place.

Metrics

CVSS 3.1

5.4/10

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

EPSS Probability

1.09%

61.2th percentile

Probability of exploitation in the next 30 days. Learn more

Affected Software

Vendor	Product	Versions
Postorius Project	Postorius	< 1.3.5

References

https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=993746Mailing List, Third Party Advisory
https://gitlab.com/mailman/postorius/-/commit/3d880c56b58bc26b32eac0799407d74b64b7474bPatch, Third Party Advisory
https://gitlab.com/mailman/postorius/-/issues/531Exploit, Issue Tracking, Patch, Third Party Advisory
https://gitlab.com/mailman/postorius/-/tagsThird Party Advisory
https://phabricator.wikimedia.org/T289798Exploit, Patch, Third Party Advisory
https://www.debian.org/security/2021/dsa-4970Third Party Advisory
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=993746Mailing List, Third Party Advisory
https://gitlab.com/mailman/postorius/-/commit/3d880c56b58bc26b32eac0799407d74b64b7474bPatch, Third Party Advisory
https://gitlab.com/mailman/postorius/-/issues/531Exploit, Issue Tracking, Patch, Third Party Advisory
https://gitlab.com/mailman/postorius/-/tagsThird Party Advisory
https://phabricator.wikimedia.org/T289798Exploit, Patch, Third Party Advisory
https://www.debian.org/security/2021/dsa-4970Third Party Advisory

Timeline

Published: Sep 10, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-40347?

How severe is CVE-2021-40347?

CVE-2021-40347 has a CVSS score of 5.4/10 (MEDIUM severity). The EPSS model estimates a 1.09% probability of exploitation in the next 30 days.

How do I fix CVE-2021-40347?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-40347?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST