CVE-2026-4274

Mattermost versions 11.2.x <= 11.2.2, 10.11.x <= 10.11.10, 11.4.x <= 11.4.0, 11.3.x <= 11.3.1 fail to restrict team-level access when processing membership sync from a remote cluster, which allows a malicious remote cluster to grant a user access to an entire private team instead of only the shared channel via sending crafted membership sync messages that trigger team membership assignment. Mattermost Advisory ID: MMSA-2026-00574

CVSS v3 5.4 MEDIUM

5.4^/10

CVSS v3 : MEDIUM

Vector :

Exploitability : 2.8 / Impact : 2.5

Attack Vector NETWORK

Attack Complexity LOW

Privileges Required LOW

User Interaction NONE

Confidentiality Impact LOW

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::::::::

History

26 Mar 2026, 18:48

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

26 Mar 2026, 11:16

Type	Values Removed	Values Added
New CVE

Information

Published : 2026-03-26 11:16

Updated : 2026-03-26 18:48

NVD link : CVE-2026-4274

Mitre link : CVE-2026-4274

CVE.ORG link : CVE-2026-4274

JSON object : View

Products Affected

mattermost

mattermost_server

CWE

CWE-863

Incorrect Authorization

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