Mastodon
CVE-2026-23961
MEDIUM
Severity by source
AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
Primary rating from GitHub Advisory · only source for this CVE.
CVSS VectorGitHub Advisory
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
Lifecycle Timeline
2DescriptionGitHub Advisory
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.
AnalysisAI
Suspended remote users in Mastodon can bypass suspension restrictions and have their posts appear in timelines through boosting and post processing logic errors. This affects all Mastodon versions for older posts, with additional bypass capabilities in versions 4.5.0-4.5.4, 4.4.5-4.4.11, 4.3.13-4.3.17, and 4.2.26-4.2.29, allowing suspended users to inject new content into the system. No patch is currently available for this integrity issue.
Technical ContextAI
Classified as CWE-863 (Incorrect Authorization). Affects Mastodon. 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. Additi
RemediationAI
Monitor vendor advisories for a patch. Restrict network access to the affected service where possible.
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Server-side request forgery in Mastodon (versions before 4.5.10, 4.4.17, and 4.3.23) lets an attacker who controls autho
Unauthenticated attackers can bypass FASP administrator approval in Mastodon 4.4.0-4.4.13 and 4.5.0-4.5.6 to subscribe t
Mastodon is a free, open-source social network server based on ActivityPub. Prior to v4.5.9, v4.4.16, and v4.3.22, Masto
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Mastodon is a free, open-source social network server based on ActivityPub. Rated high severity (CVSS 7.7), this vulnera
Same weakness CWE-863 – Incorrect Authorization
View allSame technique Authentication Bypass
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External POC / Exploit Code
Leaving vuln.today