TI-2026-17856 Aliases CVE-2026-22246

Local Mastodon users can enumerate and access severed relationships of every other local user

LOW 28CWE-201Published 2026-01-08 · Updated 2026-01-08

Key facts

Attack vector: Network
Privileges required: Low
User interaction: None
Attack complexity: Low
Impact type: Information disclosure
Confidentiality · integrity · availability: High · None · None
Fix status: Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA. Impact type from CWE-201.

Summary

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.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV

EPSS 0.00268 18th percentileScored 2026-11-07

Fix Fixed mastodon (mastodon): 4.3.17, 4.4.11, 4.5.4

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation: None
Automatable: No
Technical impact: Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

Vendor	Product	Affected versions	Fixed in	Status	Source
mastodon	mastodon	before 4.3.17; 4.4.0-beta.1 to before 4.4.11; 4.5.0-beta.1 to before 4.5.4	4.3.17, 4.4.11, 4.5.4	Patch available	CNA

mastodon Vendormastodon Affected before 4.3.17; 4.4.0-beta.1 to before 4.4.11; 4.5.0-beta.1 to before 4.5.4 Fixed in 4.3.17, 4.4.11, 4.5.4 Patch available CNA

CPE configurations NVD · 1

CPE	Versions	Role	Vendor
cpe:2.3:a:joinmastodon:mastodon::::::::	before 4.3.17; 4.4.0 to before 4.4.11; 4.5.0 to before 4.5.4	Vulnerable	mastodon

cpe:2.3:a:joinmastodon:mastodon:*:*:*:*:*:*:*:* Versions before 4.3.17; 4.4.0 to before 4.4.11; 4.5.0 to before 4.5.4 Vulnerable ·mastodon

Remediation

Fix · CNA mastodon (mastodon) Fixed in 4.3.17, 4.4.11, 4.5.4

Timeline

2026-10-02 Threatist record created from CVE-2026-22246

References

Patch 3

Advisory 1

https://github.com/mastodon/mastodon/security/advisories/GHSA-ww85-x9cp-5v24

TI-2022-02004 Improper Restriction of Excessive Authentication Attempts in mastodon/mastodon CVSS 3.1CRITICAL 9.8
TI-2025-34613 Mastodon e‑mail throttle misconfiguration allows unlimited email confirmations against unconfirmed emails CVSS 3.1HIGH 7.5
TI-2022-22936 Mastodon through 4.0.2 allows attackers to cause a denial of service (large Sidekiq pull… CVSS 3.1HIGH 7.5
TI-2023-18301 Mastodon vulnerable to arbitrary file creation through media attachments CVSS 3.1CRITICAL 10.0
TI-2023-13359 Mastodon's blind LDAP injection in login allows the attacker to leak arbitrary attributes from LDAP database CVSS 3.1HIGH 7.7
TI-2024-16846 External OpenID Connect Account Takeover by E-Mail Change in mastodon CVSS 3.1HIGH 7.4

See all 41 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences