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CVE-2026-23962

Mastodon vulnerable to Denial of Service from a single post (client/server)

Published: Jan 22, 2026Updated: Feb 2, 2026 Sources: CVE List NVDCWE-770
NVD MITRE
7.5CVSSHIGH
EPSS Score
0.5%
Top 62.0%
CISA KEV
Not in KEV
Exploits
No Known Exploits
Remediation
Patch Available

Description

Mastodon is a free, open-source social network server based on ActivityPub. Mastodon versions before v4.3.18, v4.4.12, and v4.5.5 do not have a limit on the maximum number of poll options for remote posts, allowing attackers to create polls with a very large amount of options, greatly increasing resource consumption. Depending on the number of poll options, an attacker can cause disproportionate resource usage in both Mastodon servers and clients, potentially causing Denial of Service either server-side or client-side. Mastodon versions v4.5.5, v4.4.12, v4.3.18 are patched.

CVSS Vector Breakdown

AV:NAC:LPR:NUI:NS:UC:NI:NA:H
Exploitability
AV:NAttack Vector
Network
AC:LAttack Complexity
Low
PR:NPrivileges Required
None
UI:NUser Interaction
None
Scope
S:UScope
Unchanged
Impact
C:NConfidentiality
None
I:NIntegrity
None
A:HAvailability
High
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Weaknesses

CWE-770

Affected Products

mastodonjoinmastodon
On-prem
Communications / messaging-chat
mastodonmastodon
On-prem
Communications / messaging-chat
joinmastodonoss-projectCommunicationsaka mastodon
mastodonoss-projectCommunicationsaka mastodon/mastodon

Attack Graph

Products CVE Techniques Tactics

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Exploitability

Official Patch Available

MITRE ATT&CK

1 technique
Impact
View detailed technique mapping

References

https://github.com/mastodon/mastodon/releases/tag/v4.3.18
github.com
https://github.com/mastodon/mastodon/releases/tag/v4.4.12
github.com
https://github.com/mastodon/mastodon/releases/tag/v4.5.5
github.com
and 1 more references View all →

Timeline

Published
Jan 22, 2026
Last Updated
Feb 2, 2026

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