CVE-2026-6517 PUBLISHED

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

Assigner: Mattermost
Reserved: 17.04.2026 Published: 15.06.2026 Updated: 15.06.2026

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

Metrics

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

Product Status

Vendor Mattermost
Product Mattermost
Versions Default: unaffected
  • affected from 0 to 5.5.13 (incl.)
  • Version 6.2.0 is unaffected
  • Version 5.13.6.0 is unaffected

Solutions

Update Mattermost Desktop App to versions 6.2.0, 5.13.6.0 or higher.

Credits

  • falke finder

References

Problem Types

  • CWE-522: Insufficiently Protected Credentials CWE