CVE-2026-6517

Summary

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 Software

VendorProductVersion RangeStatus
MattermostMattermost0 <= 5.5.13affected
MattermostMattermost6.2.0unaffected
MattermostMattermost5.13.6.0unaffected

Weaknesses

  • CWE-522: CWE-522: Insufficiently Protected Credentials

ADP Enrichment

CISA ADP Vulnrichment

  • SSVC:
  • Exploitation: none
    • Automatable: no
    • Technical Impact: partial

References