CVE-2026-24458: Mattermost Server

High severity, CVSS 7.5. EPSS: 0.3% chance of exploitation in the next 30 days.

Mattermost versions 11.3.x <= 11.3.0, 11.2.x <= 11.2.2, 10.11.x <= 10.11.10 fail to properly handle very long passwords, which allows an attacker to overload the server CPU and memory via executing login attempts with multi-megabyte passwords. Mattermost Advisory ID: MMSA-2026-00587

Affected products

• Mattermost Mattermost Server: from 10.11.0, before 10.11.11 (fixed in 10.11.11); from 11.2.0, before 11.2.3 (fixed in 11.2.3); from 11.3.0, before 11.3.1 (fixed in 11.3.1)

Published 2026-03-16. Last modified 2026-06-17.