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CVE-2026-6340 Details

Description

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

Metrics

CVSS 3.x Severity and Vector Strings:

NIST: [email protected]CVSS-B:6.5 MEDIUMVector:CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

CNA: [email protected]CVSS-B:4.3 MEDIUMVector:CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L

References to Advisories, Solutions, and Tools

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URL	Source(s)	Tag(s)
https://mattermost.com/security-updates	[email protected]	Vendor Advisory

Weakness Enumeration

CWE-ID	CWE Name	Source
CWE-789	Memory Allocation with Excessive Size Value	[email protected]

Affected Products

Product	Versions
mattermost mattermost server	>= 10.11.0, < 10.11.14 >= 11.4.0, < 11.4.4 >= 11.5.0, < 11.5.2
CPE cpe:2.3:a:mattermost:mattermost_server:::::::: Remediation No remediation found in references.

Change History

4 change records found show changes

Date	Action	Recorded By
Jun 17, 2026	CVE Modified	[email protected]
Jun 17, 2026	CVE Modified	CISA-ADP
May 19, 2026	Initial Analysis	[email protected]
May 18, 2026	New CVE Received	[email protected]