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CVE-2026-21388

MEDIUM CVSS 3.1: 6.5 EPSS 0.05%
Updated Apr 17, 2026
Mattermost
Parameter Value
CVSS 6.5 (MEDIUM)
Affected Versions before 2.3.2.0
Fixed In 2.3.2.0
Type CWE-770 (Allocation Without Limits)
Vendor Mattermost
Public PoC No

Mattermost Plugins versions <=2.3.1 fail to limit the request body size on the {{/lifecycle}} webhook endpoint which allows an authenticated attacker to cause memory exhaustion and denial of service via sending an oversized JSON payload. Mattermost Advisory ID: MMSA-2026-00610

Attack Parameters

Attack Vector
Network
Can be exploited remotely
Attack Complexity
Low
Easy to exploit
Privileges Required
Low
Basic privileges needed
User Interaction
None
No user interaction needed

Impact Assessment

Confidentiality
None
No data leak
Integrity
None
No data modification
Availability
High
Complete denial of service

CVSS Vector v3.1

Vulnerable Products 1

Configuration From (including) Up to (excluding)
Mattermost Mattermost
cpe:2.3:a:mattermost:mattermost:*:*:*:*:*:*:*:*
2.3.2.0