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.
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | postorius | 1.3.5-1 | — |
| Debian 13 | postorius | 1.3.5-1 | — |
| Debian 12 | postorius | 1.3.5-1 | — |
| Debian 11 | postorius | 1.3.4-2+deb11u1 | DSA-4970-1 |
| Debian 10 | postorius | 1.2.4-1+deb10u1 | DSA-4970-1 |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 22.04 LTS | postorius | 1.3.5-1 | — |
| Ubuntu 20.04 LTS | postorius | 1.2.4-1ubuntu0.1 | USN-5157-1 |
| Ubuntu 18.04 LTS | postorius | 1.1.2-3ubuntu0.1 | USN-5157-1 |
Affected packages
| Ecosystem | Package | Affected | Fixed | Record |
|---|---|---|---|---|
| PyPI | postorius | < 1.3.5 | 1.3.5 | GHSA-v83x-78q3-gr2j |
Advisories 2
- DSA-4970-1 postorius - security update Debian Security (DSA / DLA) · Mar 9, 2026
- USN-5157-1 postorius vulnerability Ubuntu Security Notices (USN) · Feb 10, 2026
References
- https://gitlab.com/mailman/postorius/-/issues/531
- https://phabricator.wikimedia.org/T289798
- https://gitlab.com/mailman/postorius/-/tags
- DSA-4970 vendor-advisory
- https://gitlab.com/mailman/postorius/-/commit/3d880c56b58bc26b32eac0799407d74b64b7474b
- https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=993746