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MEDIUM · 6.3

CVE-2026-6517

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 wi...

Vulnerability 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

CVSS Score

6.3

MEDIUM

CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:N/A:N
Attack Vector
NETWORK
Attack Complexity
HIGH
Privileges Required
LOW
User Interaction
NONE
Scope
CHANGED
Confidentiality
HIGH
Integrity
NONE
Availability
NONE

Affected Products

VendorProductVersions
MattermostMattermost Desktop<= 5.13.0

Related Weaknesses (CWE)

CWE-522

References

FAQ

What is CVE-2026-6517?

CVE-2026-6517 is a vulnerability with a CVSS score of 6.3 (MEDIUM). 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 wi...

How severe is CVE-2026-6517?

CVE-2026-6517 has been rated MEDIUM with a CVSS base score of 6.3/10. Review the CVSS metrics above for detailed severity breakdown.

Is there a patch for CVE-2026-6517?

Check the references section above for vendor advisories and patch information. Affected products include: Mattermost Mattermost Desktop.