CVE-2026-23961

5.3 MEDIUM
Published: January 22, 2026 Modified: February 02, 2026
View on NVD

Description

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.

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CVSS v3.x Details

0.0 Low Medium High Critical 10.0
Vector String
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

References to Advisories, Solutions, and Tools

Patch Vendor Advisory Exploit Third Party Advisory
https://github.com/mastodon/mastodon/releases/tag/v4.3.18
Source: security-advisories@github.com
Release Notes
https://github.com/mastodon/mastodon/releases/tag/v4.4.12
Source: security-advisories@github.com
Release Notes
https://github.com/mastodon/mastodon/releases/tag/v4.5.5
Source: security-advisories@github.com
Release Notes
https://github.com/mastodon/mastodon/security/advisories/GHSA-5h2f-wg8j-xqwp
Source: security-advisories@github.com
Vendor Advisory

4 reference(s) from NVD

Quick Stats

CVSS v3 Score
5.3 / 10.0
EPSS (Exploit Probability)
0.0%
5th percentile
Exploitation Status
Not in CISA KEV

Weaknesses (CWE)

Affected Vendors

joinmastodon