CVE-2026-23962

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

State: Published
Severity: 7.5 High
Published: Jan 22, 2026
Updated: Jan 22, 2026
Reserved: Jan 19, 2026

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.

Scores

CVSS	Score	Vector	Source
3.1	7.5 High	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H	GitHub_M

Weaknesses

CWE-770 Allocation of Resources Without Limits or Throttling

Affected Products

Product	Versions
mastodonmastodon	< 4.3.18Affected >= 4.4.0, < 4.4.12Affected >= 4.5.0, < 4.5.5Affected

References

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