CVE-2026-6517 MEDIUM

CVE-2026-6517: Mattermost Desktop App fails to restrict the allow list of domains which NTLM credentials are passed

Vendor Mattermost
Product Mattermost
Weakness CWE-522 · Insufficiently protected credentials
Published June 15, 2026
Last update June 15, 2026
View on NVD All CVEs

CVSS base score

6.3/10
Attack vector Network
Attack complexity High
Privileges required Low
User interaction None
Confidentiality High
Integrity None

CVSS vector

CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:N/A:N

What the vulnerability does

01Description

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

Key dates

02Disclosure timeline

June 15, 2026 CVE published
June 15, 2026 Record updated