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Vulnerability · Published Jan 8, 2026 · Assigned by GitHub_M

CVE-2026-22246Local Mastodon users can enumerate and access severed relationships of every other local user

Medium 6.5

In plain English

A medium-severity security flaw in mastodon from mastodon. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 19% of all known vulnerabilities).

Severity (CVSS 3.1)6.5Medium
Exploit odds (30 days)0.3%top 81.0% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official 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.

Affected products (as reported)

VendorProductVersions
mastodon mastodon < 4.3.17>= 4.4.0-beta.1, < 4.4.11>= 4.5.0-beta.1, < 4.5.4

Weakness: CWE-201 · Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N

References