CVE-2017-18906: Mattermost Server

High severity, CVSS 8.1. EPSS: 0.8% chance of exploitation in the next 30 days.

An issue was discovered in Mattermost Server before 4.0.0, 3.10.2, and 3.9.2, when Single Sign-On OAuth2 is used. An attacker could claim somebody else's account.

Affected products

• Mattermost Mattermost Server: before 3.9.2 (fixed in 3.9.2); from 3.10.0, before 3.10.2 (fixed in 3.10.2)

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