Vulnerability DatabaseCVE-2026-4274
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CVE-2026-4274
March 26, 2026
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
Affected Packages
github.com/mattermost/mattermost (GO):
Affected version(s) =v11.4.0 <v11.4.1
Fix Suggestion:
Update to version v11.4.1
github.com/mattermost/mattermost (GO):
Affected version(s) >=v10.11.0 <v10.11.11
Fix Suggestion:
Update to version v10.11.11
github.com/mattermost/mattermost (GO):
Affected version(s) >=v11.2.0 <v11.2.3
Fix Suggestion:
Update to version v11.2.3
github.com/mattermost/mattermost (GO):
Affected version(s) =v11.4.0 <v11.4.1
Fix Suggestion:
Update to version v11.4.1
github.com/mattermost/mattermost (GO):
Affected version(s) >=v11.3.0 <v11.3.2
Fix Suggestion:
Update to version v11.3.2
github.com/mattermost/mattermost (GO):
Affected version(s) >=v11.2.0 <v11.2.3
Fix Suggestion:
Update to version v11.2.3
github.com/mattermost/mattermost (GO):
Affected version(s) >=v10.11.0 <v10.11.11
Fix Suggestion:
Update to version v10.11.11
github.com/mattermost/mattermost (GO):
Affected version(s) =v11.4.0 <v11.4.1
Fix Suggestion:
Update to version v11.4.1
github.com/mattermost/mattermost (GO):
Affected version(s) >=v11.2.0 <v11.2.3
Fix Suggestion:
Update to version v11.2.3
github.com/mattermost/mattermost (GO):
Affected version(s) >=v11.3.0 <v11.3.2
Fix Suggestion:
Update to version v11.3.2
github.com/mattermost/mattermost (GO):
Affected version(s) =v11.4.0 <v11.4.1
Fix Suggestion:
Update to version v11.4.1
github.com/mattermost/mattermost (GO):
Affected version(s) >=v11.3.0 <v11.3.2
Fix Suggestion:
Update to version v11.3.2
github.com/mattermost/mattermost (GO):
Affected version(s) >=v11.3.0 <v11.3.2
Fix Suggestion:
Update to version v11.3.2
github.com/mattermost/mattermost (GO):
Affected version(s) >=v11.2.0 <v11.2.3
Fix Suggestion:
Update to version v11.2.3
github.com/mattermost/mattermost (GO):
Affected version(s) >=v11.3.0 <v11.3.2
Fix Suggestion:
Update to version v11.3.2
github.com/mattermost/mattermost (GO):
Affected version(s) >=v10.11.0 <v10.11.11
Fix Suggestion:
Update to version v10.11.11
github.com/mattermost/mattermost (GO):
Affected version(s) >=v10.11.0 <v10.11.11
Fix Suggestion:
Update to version v10.11.11
github.com/mattermost/mattermost (GO):
Affected version(s) >=v11.2.0 <v11.2.3
Fix Suggestion:
Update to version v11.2.3
github.com/mattermost/mattermost (GO):
Affected version(s) >=v10.11.0 <v10.11.11
Fix Suggestion:
Update to version v10.11.11
github.com/mattermost/mattermost (GO):
Affected version(s) =v11.4.0 <v11.4.1
Fix Suggestion:
Update to version v11.4.1
Related Resources (1)
https://mattermost.com/security-updates
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CVSS v4
Base Score:
5.3
Attack Vector
NETWORK
Attack Complexity
LOW
Attack Requirements
NONE
Privileges Required
LOW
User Interaction
NONE
Vulnerable System Confidentiality
LOW
Vulnerable System Integrity
LOW
Vulnerable System Availability
NONE
Subsequent System Confidentiality
NONE
Subsequent System Integrity
NONE
Subsequent System Availability
NONE
CVSS v3
Base Score:
5.4
Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
LOW
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
LOW
Integrity
LOW
Availability
NONE
Weakness Type (CWE)
Incorrect Authorization
CWE-863
EPSS
Base Score:
0.03