CVE-2017-18871: Mattermost Server

High severity, CVSS 7.5. EPSS: 1.1% chance of exploitation in the next 30 days.

An issue was discovered in Mattermost Server before 4.5.0, 4.4.5, 4.3.4, and 4.2.2. It allows attackers to cause a denial of service (application crash) via an @ character before a JavaScript field name.

Affected products

• Mattermost Mattermost Server: before 4.2.2 (fixed in 4.2.2); from 4.3.0, before 4.3.4 (fixed in 4.3.4); from 4.4.0, before 4.4.5 (fixed in 4.4.5); version 4.5.0 only

Published 2020-06-19. Last modified 2026-06-17.