CVE-2026-23961
January 22, 2026
Mastodon is a free, open-source social network server based on ActivityPub. Mastodon allows server administrators to suspend remote users to prevent interactions. However, some logic errors allow already-known posts from such suspended users to appear in timelines if boosted. Furthermore, under certain circumstances, previously-unknown posts from suspended users can be processed. This issue allows old posts from suspended users to occasionally end up on timelines on all Mastodon versions. Additionally, on Mastodon versions from v4.5.0 to v4.5.4, v4.4.5 to v4.4.11, v4.3.13 to v4.3.17, and v4.2.26 to v4.2.29, remote suspended users can partially bypass the suspension to get new posts in. Mastodon versions v4.5.5, v4.4.12, v4.3.18 are patched.
Affected Packages
https://github.com/mastodon/mastodon.git (GITHUB):
Affected version(s) >=v4.4.0 <v4.4.12Fix Suggestion:
Update to version v4.4.12https://github.com/mastodon/mastodon.git (GITHUB):
Affected version(s) >=v0.1.0 <v4.3.18Fix Suggestion:
Update to version v4.3.18https://github.com/mastodon/mastodon.git (GITHUB):
Affected version(s) >=v4.5.0 <v4.5.5Fix Suggestion:
Update to version v4.5.5Related Resources (4)
Do you need more information?
Contact UsCVSS v4
Base Score:
6.9
Attack Vector
NETWORK
Attack Complexity
LOW
Attack Requirements
NONE
Privileges Required
NONE
User Interaction
NONE
Vulnerable System Confidentiality
NONE
Vulnerable System Integrity
LOW
Vulnerable System Availability
NONE
Subsequent System Confidentiality
NONE
Subsequent System Integrity
NONE
Subsequent System Availability
NONE
CVSS v3
Base Score:
5.3
Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
NONE
Integrity
LOW
Availability
NONE
Weakness Type (CWE)
Incorrect Authorization
EPSS
Base Score:
0.02
