Vulnerability Details 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 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
Exploit prediction scoring system (EPSS) score
EPSS Score 0.002
EPSS Ranking 8.3%
CVSS Severity
CVSS v3 Score 6.3
References
Products affected by CVE-2026-6517
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cpe:2.3:a:mattermost:mattermost_desktop:1.3.0
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cpe:2.3:a:mattermost:mattermost_desktop:4.2.2
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cpe:2.3:a:mattermost:mattermost_desktop:4.2.3
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cpe:2.3:a:mattermost:mattermost_desktop:4.3.0
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cpe:2.3:a:mattermost:mattermost_desktop:4.3.2
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cpe:2.3:a:mattermost:mattermost_desktop:4.4.0
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cpe:2.3:a:mattermost:mattermost_desktop:4.4.1
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cpe:2.3:a:mattermost:mattermost_desktop:4.4.2
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cpe:2.3:a:mattermost:mattermost_desktop:4.5.0
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cpe:2.3:a:mattermost:mattermost_desktop:4.5.1
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cpe:2.3:a:mattermost:mattermost_desktop:4.5.2
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cpe:2.3:a:mattermost:mattermost_desktop:4.5.3
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cpe:2.3:a:mattermost:mattermost_desktop:4.5.4
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cpe:2.3:a:mattermost:mattermost_desktop:4.6.0
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cpe:2.3:a:mattermost:mattermost_desktop:4.6.1
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cpe:2.3:a:mattermost:mattermost_desktop:4.6.2
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cpe:2.3:a:mattermost:mattermost_desktop:4.7.0
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cpe:2.3:a:mattermost:mattermost_desktop:4.7.1
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cpe:2.3:a:mattermost:mattermost_desktop:4.7.2
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cpe:2.3:a:mattermost:mattermost_desktop:5.0.0
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cpe:2.3:a:mattermost:mattermost_desktop:5.0.1
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cpe:2.3:a:mattermost:mattermost_desktop:5.0.2
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cpe:2.3:a:mattermost:mattermost_desktop:5.0.3
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cpe:2.3:a:mattermost:mattermost_desktop:5.0.4
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cpe:2.3:a:mattermost:mattermost_desktop:5.1.0
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cpe:2.3:a:mattermost:mattermost_desktop:5.1.1
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cpe:2.3:a:mattermost:mattermost_desktop:5.10.0
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cpe:2.3:a:mattermost:mattermost_desktop:5.10.1
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cpe:2.3:a:mattermost:mattermost_desktop:5.10.2
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cpe:2.3:a:mattermost:mattermost_desktop:5.11.0
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cpe:2.3:a:mattermost:mattermost_desktop:5.11.1
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cpe:2.3:a:mattermost:mattermost_desktop:5.11.2
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cpe:2.3:a:mattermost:mattermost_desktop:5.11.3
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cpe:2.3:a:mattermost:mattermost_desktop:5.12.0
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cpe:2.3:a:mattermost:mattermost_desktop:5.12.1
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cpe:2.3:a:mattermost:mattermost_desktop:5.13.0
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cpe:2.3:a:mattermost:mattermost_desktop:5.2.0
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cpe:2.3:a:mattermost:mattermost_desktop:5.2.1
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cpe:2.3:a:mattermost:mattermost_desktop:5.2.2
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cpe:2.3:a:mattermost:mattermost_desktop:5.3.1
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cpe:2.3:a:mattermost:mattermost_desktop:5.4.0
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cpe:2.3:a:mattermost:mattermost_desktop:5.5.0
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cpe:2.3:a:mattermost:mattermost_desktop:5.5.1
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cpe:2.3:a:mattermost:mattermost_desktop:5.6.0
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cpe:2.3:a:mattermost:mattermost_desktop:5.7.0
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cpe:2.3:a:mattermost:mattermost_desktop:5.8.0
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cpe:2.3:a:mattermost:mattermost_desktop:5.8.1
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cpe:2.3:a:mattermost:mattermost_desktop:5.9.0
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cpe:2.3:a:mattermost:mattermost_desktop:5.9.1
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cpe:2.3:a:mattermost:mattermost_desktop:5.9.2
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cpe:2.3:a:mattermost:mattermost_desktop:6.1.0