CVE-2026-10819: Mattermost Server

Medium severity, CVSS 6.5. EPSS: 0.4% chance of exploitation in the next 30 days.

Mattermost versions 11.6.x <= 11.6.5, 10.11.x <= 10.11.20, 11.8.x <= 11.8.1, 11.7.x <= 11.7.4 fail to limit the number of frames and enforce the file size cap on animated GIF uploads, which allows an authenticated attacker to cause a denial of service via a crafted animated GIF uploaded as a custom emoji.. Mattermost Advisory ID: MMSA-2026-00695

Affected products

• Mattermost Mattermost Server: from 10.11.0, before 10.11.21 (fixed in 10.11.21); from 11.6.0, before 11.6.6 (fixed in 11.6.6); from 11.7.0, before 11.7.5 (fixed in 11.7.5); from 11.8.0, before 11.8.2 (fixed in 11.8.2)

Published 2026-07-27. Last modified 2026-08-03.