High severity · published Jan 22, 2026
CVE-2026-23962
Mastodon vulnerable to Denial of Service from a single post (client/server)
7.5
CVSS
0.5%
EPSS
No
On KEV
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
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
None
Integrity
None
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.5% · higher than 46% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
MA
mastodon · mastodon
< 4.3.18; >= 4.4.0, < 4.4.12; >= 4.5.0, < 4.5.5 · source: vendor, NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-23962
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-23962
Release Notes
https://github.com/mastodon/mastodon/releases/tag/v4.3.18
Release Notes
https://github.com/mastodon/mastodon/releases/tag/v4.4.12
Release Notes
https://github.com/mastodon/mastodon/releases/tag/v4.5.5
Vendor Advisory
https://github.com/mastodon/mastodon/security/advisories/GHSA-gg8q-rcg7-p79g
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