CVE-2026-6517
Medium
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
SeverityMedium
CVSS6.3
Exploit probability—
Product
Mattermost Desktop
PublishedJun 15, 2026
First seenJun 15, 2026
Weakness typeCWE-522CWE-522
How to fix
Vendor advisories
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| mattermost mattermost_desktop | v ≤ 5.13.0, 6.1.0 ≤ v ≤ 6.1.5 | — |
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