CVE-2026-18799

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

CVSS v3 4.3 MEDIUM

4.3^/10

CVSS v3 : MEDIUM

Vector :

Exploitability : 2.8 / Impact : 1.4

Attack Vector NETWORK

Attack Complexity LOW

Privileges Required LOW

User Interaction NONE

Confidentiality Impact NONE

Integrity Impact LOW

Availability Impact NONE

Scope UNCHANGED

References

Link	Resource
https://mattermost.com/security-updates	Vendor Advisory

Configurations

Configuration 1 (hide)

OR	cpe:2.3:a:mattermost:mattermost_server::::::::
	cpe:2.3:a:mattermost:mattermost_server::::::::
	cpe:2.3:a:mattermost:mattermost_server::::::::
	cpe:2.3:a:mattermost:mattermost_server:11.10.0:::::::*

History

29 Oct 2026, 18:08

Type	Values Removed	Values Added
CPE		cpe:2.3:a:mattermost:mattermost_server:11.10.0:::::::* cpe:2.3:a:mattermost:mattermost_server::::::::
References	~~() https://mattermost.com/security-updates -~~	() https://mattermost.com/security-updates - Vendor Advisory
First Time		Mattermost mattermost Server Mattermost

16 Oct 2026, 08:17

Type	Values Removed	Values Added
New CVE

Information

Published : 2026-10-16 08:17

Updated : 2026-10-29 18:08

NVD link : CVE-2026-18799

Mitre link : CVE-2026-18799

CVE.ORG link : CVE-2026-18799

JSON object : View

Products Affected

mattermost

mattermost_server

CWE

CWE-862

Missing Authorization

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