Mattermost Desktop App versions <=6.1 5.5.13.0 fail to restrict the allow list of domains to which NTLM credentials were forwarded to in the Mattermost Desktop App which allows any user on a server without the image proxy enabled to intercept other users credentials via embedding an image that routes to an external web server. Mattermost Advisory ID: MMSA-2026-00651

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Advisories

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Fixes

Solution

Update Mattermost Desktop App to versions 6.2.0, 5.13.6.0 or higher.


Workaround

No workaround given by the vendor.

References
History

Tue, 16 Jun 2026 17:00:00 +0000

Type Values Removed Values Added
First Time appeared Mattermost mattermost Desktop
CPEs cpe:2.3:a:mattermost:mattermost_desktop:*:*:*:*:*:*:*:*
cpe:2.3:a:mattermost:mattermost_desktop:*:-:*:*:*:*:*:*
Vendors & Products Mattermost mattermost Desktop

Tue, 16 Jun 2026 09:15:00 +0000

Type Values Removed Values Added
First Time appeared Mattermost
Mattermost mattermost
Vendors & Products Mattermost
Mattermost mattermost

Mon, 15 Jun 2026 16:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Mon, 15 Jun 2026 14:00:00 +0000

Type Values Removed Values Added
Description Mattermost Desktop App versions <=6.1 5.5.13.0 fail to restrict the allow list of domains to which NTLM credentials were forwarded to in the Mattermost Desktop App which allows any user on a server without the image proxy enabled to intercept other users credentials via embedding an image that routes to an external web server. Mattermost Advisory ID: MMSA-2026-00651
Title Mattermost Desktop App fails to restrict the allow list of domains which NTLM credentials are passed
Weaknesses CWE-522
References
Metrics cvssV3_1

{'score': 6.3, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:N/A:N'}


Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: Mattermost

Published:

Updated: 2026-06-15T16:00:00.919Z

Reserved: 2026-04-17T14:25:10.246Z

Link: CVE-2026-6517

cve-icon Vulnrichment

Updated: 2026-06-15T15:59:52.206Z

cve-icon NVD

Status : Analyzed

Published: 2026-06-15T14:16:37.910

Modified: 2026-06-16T16:54:47.653

Link: CVE-2026-6517

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-06-17T02:45:02Z

Weaknesses