Vulnerability DatabaseCVE-2026-6340
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CVE-2026-6340
Published:May 18, 2026
Updated:June 11, 2026
Mattermost versions 11.5.x <= 11.5.1, 10.11.x <= 10.11.13, 11.4.x <= 11.4.3 fail to validate 7zip archive structure before processing which allows an authenticated attacker to cause server memory exhaustion and denial of service via uploading a specially crafted 7zip file with excessive folder declarations.. Mattermost Advisory ID: MMSA-2026-00573
Affected Packages
https://github.com/mattermost/mattermost.git (GITHUB):
Affected version(s) >=v10.11.0 <v10.11.14
Fix Suggestion:
Update to version v10.11.14
https://github.com/mattermost/mattermost.git (GITHUB):
Affected version(s) >=v11.4.0 <v11.4.4
Fix Suggestion:
Update to version v11.4.4
https://github.com/mattermost/mattermost.git (GITHUB):
Affected version(s) >=v11.5.0 <v11.5.2
Fix Suggestion:
Update to version v11.5.2
github.com/mattermost/mattermost (GO):
Affected version(s) >=v11.5.0 <v11.5.2
Fix Suggestion:
Update to version v11.5.2
github.com/mattermost/mattermost (GO):
Affected version(s) >=v11.4.0 <v11.4.4
Fix Suggestion:
Update to version v11.4.4
github.com/mattermost/mattermost/server/v8 (GO):
Affected version(s) >=v8.0.0-20230429093631-aac4f2337933 <v8.0.0-20260325191733-fb11968f8798
Fix Suggestion:
Update to version v8.0.0-20260325191733-fb11968f8798
github.com/mattermost/mattermost (GO):
Affected version(s) >=v10.11.0 <v10.11.14
Fix Suggestion:
Update to version v10.11.14
Related Resources (4)
https://github.com/mattermost/mattermost
https://github.com/mattermost/mattermost/commit/fb11968f8798925c7b75711025bc5f991124ba26
https://nvd.nist.gov/vuln/detail/CVE-2026-6340
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
NONE
Vulnerable System Integrity
NONE
Vulnerable System Availability
LOW
Subsequent System Confidentiality
NONE
Subsequent System Integrity
NONE
Subsequent System Availability
NONE
CVSS v3
Base Score:
4.3
Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
LOW
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
NONE
Integrity
NONE
Availability
LOW
Weakness Type (CWE)
Memory Allocation with Excessive Size Value
CWE-789
EPSS
Base Score:
0.05