CVE-2026-6517

MEDIUM

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

Title source: cna
STIX 2.1

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

References (1)

Core 1
Core References
Vendor Advisory vendor-advisory
MMSA-2026-00651
https://mattermost.com/security-updates

Scores

CVSS v3 6.3
Attack Vector NETWORK
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:N/A:N

CISA SSVC

Vulnrichment
Exploitation none
Automatable no
Technical Impact partial

Details

CWE
CWE-522
Status published
Products (3)
Mattermost/Mattermost < 5.5.13
Mattermost/Mattermost 5.13.6.0
Mattermost/Mattermost 6.2.0
Published Jun 15, 2026
Tracked Since Jun 15, 2026