CVE-2017-18894: 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 4.2.0, 4.1.1, and 4.0.5, when used as an OAuth 2.0 service provider. Sometimes. resource-owner authorization is bypassed, allowing account takeover.

Affected products

• Mattermost Mattermost Server: before 4.0.5 (fixed in 4.0.5); from 4.1.0, before 4.1.1 (fixed in 4.1.1); version 4.2.0 only

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