CVE-2026-6517mediumCWE-522

CVE-2026-6517: medium-severity vulnerability in Mattermost

Mattermost Desktop App fails to restrict the allow list of domains which NTLM credentials are passed

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13Vexday Risk Score

No sign of exploitation. No public exploitation artifact known so far.

ssvc Trackcvss 6.3epss 0.2%
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:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:N/A:N
Affected products
Mattermost · Mattermost
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