Login Request a demo
Medium severity · published Sep 10, 2021
CVE-2021-40347
An issue was discovered in views/list.py in GNU Mailman Postorius before 1.3.5
5.4
CVSS
1.2%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N
Attack vector
Network
Complexity
Low
Privileges
Low
User interaction
None
Confidentiality
Low
Integrity
Low
Availability
None
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)1.2% · higher than 68% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
PO
Postorius · Postorius Project
before 1.3.5 · source: NVD
Affected product
PO
Postorius
Postorius Project
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2021-40347
CVE.org
https://www.cve.org/CVERecord?id=CVE-2021-40347
Mailing List
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=993746
Patch
https://gitlab.com/mailman/postorius/-/commit/3d880c56b58bc26b32eac0799407d74b64b7474b
Exploit
https://gitlab.com/mailman/postorius/-/issues/531
Third Party Advisory
https://gitlab.com/mailman/postorius/-/tags
Exploit
https://phabricator.wikimedia.org/T289798
Third Party Advisory
https://www.debian.org/security/2021/dsa-4970
More from Postorius
6.1
CVE-2026-44742
Postorius through 1.3.13 does not escape HTML in the message subject when rendering it in the Held messages pop-up, as exploited in the wild in May 2026