CVE-2026-22246
Mastodon 4.3 added notifications of severed relationships, allowing end-users to inspect the relationships they lost as the result of a moderation action.
Does this matter?
Lower severity and a low EPSS score (0.26%). Track it; it rarely justifies an emergency change on its own.
Description
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.
- CVSS 3.1
- 4.3 MEDIUMCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
- EPSS
- 0.26% probability · 18th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-201
- Affected
- joinmastodon/mastodon
- Source
- security-advisories@github.com
References
- https://github.com/mastodon/mastodon/commit/68e30985ca7afdb89af1b2e9dc962e1993dc8076Patch
- https://github.com/mastodon/mastodon/commit/b2bcd34486fd6681cc0f30028086ef0f47282adfPatch
- https://github.com/mastodon/mastodon/commit/c1fb6893c5175d74c074f6f786d504c8bc610d57Patch
- https://github.com/mastodon/mastodon/security/advisories/GHSA-ww85-x9cp-5v24Third Party Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.