CVE-2026-6517
Published:June 15, 2026
Updated:June 29, 2026
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
Affected Packages
https://github.com/mattermost/desktop.git (GITHUB):
Affected version(s) >=v6.0.0 <v6.2.0Fix Suggestion:
Update to version v6.2.0https://github.com/mattermost/desktop.git (GITHUB):
Affected version(s) >=v5.13.0 <v5.13.6Fix Suggestion:
Update to version v5.13.6Related Resources (1)
Do you need more information?
Contact UsCVSS v4
Base Score:
7
Attack Vector
NETWORK
Attack Complexity
HIGH
Attack Requirements
NONE
Privileges Required
LOW
User Interaction
NONE
Vulnerable System Confidentiality
HIGH
Vulnerable System Integrity
NONE
Vulnerable System Availability
NONE
Subsequent System Confidentiality
HIGH
Subsequent System Integrity
NONE
Subsequent System Availability
NONE
CVSS v3
Base Score:
6.3
Attack Vector
NETWORK
Attack Complexity
HIGH
Privileges Required
LOW
User Interaction
NONE
Scope
CHANGED
Confidentiality
HIGH
Integrity
NONE
Availability
NONE
Weakness Type (CWE)
Insufficiently Protected Credentials
EPSS
Base Score:
0.19