CVE-2026-23961: Mastodon may allow a remote suspension bypass
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 Software
Event History
Frequently Asked Questions
What is the severity of CVE-2026-23961?
CVE-2026-23961 has a moderate severity level due to its potential to allow suspended users' posts to be viewed.
How do I fix CVE-2026-23961?
To resolve CVE-2026-23961, upgrade to the latest version of Mastodon that addresses this vulnerability.
What versions of Mastodon are affected by CVE-2026-23961?
CVE-2026-23961 affects all versions of Mastodon, specifically those between 4.2.26 and 4.5.4.
What type of vulnerability is CVE-2026-23961?
CVE-2026-23961 is a logic error vulnerability that allows for the remote suspension bypass of users.
Can users' posts from suspended accounts be still accessed due to CVE-2026-23961?
Yes, due to the vulnerability in CVE-2026-23961, already-known posts from suspended users may still appear.