PT-2020-8440 · Mattermost · Mattermost Server

Published 2020-06-19 · Updated 2026-01-17 · CVE-2017-18894

Positive Technologies (AI Summary)

CVSS v3.1

8.1

High

Base vector

AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N

Name of the Vulnerable Software and Affected Versions: Mattermost Server versions prior to 4.2.0 Mattermost Server version 4.1.1 Mattermost Server version 4.0.5

Description: An issue was discovered in Mattermost Server when used as an OAuth 2.0 service provider, where sometimes resource-owner authorization is bypassed, allowing account takeover.

Recommendations: For versions prior to 4.2.0, update to version 4.2.0 or later. For version 4.1.1, update to version 4.2.0 or later. For version 4.0.5, update to version 4.2.0 or later.

Fix

Incorrect Permission

IDOR

Weakness Enumeration

CWE-732

CWE-639

Related Identifiers

CVE-2017-18894

GHSA-GG42-MWR6-P82C

GO-2026-4297

SUSE-SU-2026:0142-1

Affected Products

Mattermost Server

References · 42

• https://osv.dev/vulnerability/GHSA-gg42-mwr6-p82c · Vendor Advisory
• https://osv.dev/vulnerability/CVE-2017-18894 · Vendor Advisory
• https://nvd.nist.gov/vuln/detail/CVE-2017-18894 · Security Note
• https://osv.dev/vulnerability/SUSE-SU-2026:0142-1 · Vendor Advisory
• https://mattermost.com/security-updates · Vendor Advisory
• https://osv.dev/vulnerability/GO-2026-4297 · Vendor Advisory
• https://github.com/mattermost/mattermost · Note
• https://suse.com/security/cve/CVE-2026-22688 · Note
• https://suse.com/security/cve/CVE-2026-21859 · Note
• https://suse.com/support/update/announcement/2026/suse-su-20260142-1 · Note
• https://suse.com/security/cve/CVE-2026-22703 · Note
• https://suse.com/security/cve/CVE-2025-68954 · Note
• https://suse.com/security/cve/CVE-2017-18905 · Note
• https://suse.com/security/cve/CVE-2017-18897 · Note
• https://t.me/cibsecurity/12913 · Telegram Post