CVE-2026-6517

EUVD-2026-36725
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
ProviderTypeBase ScoreAtk. VectorAtk. ComplexityPriv. RequiredVector
MattermostCNA
6.3 MEDIUM
NETWORK
HIGH
LOW
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:N/A:N
Base Score
CVSS 3.x
EPSS Score
Percentile: 8%
Affected Products (NVD)
VendorProductVersion
mattermostmattermost_desktop
𝑥
≤ 5.13.0
mattermostmattermost_desktop
6.1.0 ≤
𝑥
≤ 6.1.5
𝑥
= Vulnerable software versions
Early Detection
Affected products identified ahead of NVD analysis through intelligence sources.
VendorProductVersionSource
mattermostmattermost
𝑥
≤ 5.5.13
CNA
Common Weakness Enumeration
References
https://mattermost.com/security-updates