CVE-2026-22246: Local Mastodon users can enumerate and access severed relationships of every other local user
Mastodon is a free, open-source social network server based on ActivityPub. Mastodon 4.3 added notifications of severed relationships, allowing end-users to inspect the relationships they lost as the result of a moderation action. The code allowing users to download lists of severed relationships for a particular event fails to check the owner of the list before returning the lost relationships. Any registered local user can access the list of lost followers and followed users caused by any severance event, and go through all severance events this way. The leaked information does not include the name of the account which has lost follows and followers. This has been fixed in Mastodon v4.3.17, v4.4.11 and v4.5.4.
Affected Software
Remediation
Event History
Frequently Asked Questions
What is the severity of CVE-2026-22246?
CVE-2026-22246 is rated with a moderate severity due to its potential impact on user privacy.
How do I fix CVE-2026-22246?
To fix CVE-2026-22246, upgrade your Mastodon instance to version 4.3.18 or higher, or 4.4.12 or higher.
What software versions are affected by CVE-2026-22246?
CVE-2026-22246 affects Mastodon versions up to but not including 4.3.17, 4.4.11, and 4.5.4.
What are the implications of CVE-2026-22246 for users?
CVE-2026-22246 may allow unauthorized access to lists of severed relationships, compromising user privacy.
Is there a known workaround for CVE-2026-22246?
There is no known workaround for CVE-2026-22246; upgrading is the recommended solution.