Input validation error in Mastodon - CVE-2026-23962
Published: April 23, 2026
Vulnerability identifier: #VU126992
CSH Severity: Medium
CVSS v4: 8.7 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-23962
CWE-ID: CWE-20
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to cause a denial of service.
The vulnerability exists due to improper input validation in poll handling for remote posts when processing remote posts containing an excessive number of poll options. A remote attacker can create a remote post with a very large number of poll options to cause a denial of service.
The issue can cause disproportionate resource consumption in both Mastodon servers and clients.
Affected software
Mastodon
How to mitigate CVE-2026-23962
Install security update from vendor's website.
Mastodon - addressed in versions 4.3.18, 4.4.12, 4.5.5