Mattermost versions 11.10.x <= 11.10.0, 11.7.x <= 11.7.9, 11.9.x <= 11.9.1, 11.8.x <= 11.8.5 fail to restrict Slack import account binding to system administrator-initiated imports which allows an authenticated attacker with team admin privileges to force-add existing Mattermost users to their team and forge posts attributed to those users' identities via a crafted Slack export containing target users' email addresses.. Mattermost Advisory ID: MMSA-2026-00757
References
History

Sat, 17 Oct 2026 16:45:00 +0000

Type Values Removed Values Added
First Time appeared Mattermost
Mattermost mattermost
Vendors & Products Mattermost
Mattermost mattermost

Fri, 16 Oct 2026 12:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Fri, 16 Oct 2026 07:30:00 +0000

Type Values Removed Values Added
Description Mattermost versions 11.10.x <= 11.10.0, 11.7.x <= 11.7.9, 11.9.x <= 11.9.1, 11.8.x <= 11.8.5 fail to restrict Slack import account binding to system administrator-initiated imports which allows an authenticated attacker with team admin privileges to force-add existing Mattermost users to their team and forge posts attributed to those users' identities via a crafted Slack export containing target users' email addresses.. Mattermost Advisory ID: MMSA-2026-00757
Title Mattermost Server fails to restrict Slack import account binding, allowing team admins to forge posts as existing users
Weaknesses CWE-862
References
Metrics cvssV3_1

{'score': 4.3, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N'}


cve-icon MITRE

Status: PUBLISHED

Assigner: Mattermost

Published: 2026-10-16T07:16:19.062Z

Updated: 2026-10-16T11:28:45.200Z

Reserved: 2026-08-04T10:05:23.880Z

Link: CVE-2026-18799

cve-icon Vulnrichment

Updated: 2026-10-16T11:28:40.139Z

cve-icon NVD

Status : Awaiting Analysis

Published: 2026-10-16T08:17:13.073

Modified: 2026-10-16T19:23:18.623

Link: CVE-2026-18799

cve-icon Redhat

No data.