PT-2026-49238 · Mattermost · Mattermost

Falke · Published 2026-06-15 · Updated 2026-06-15 · CVE-2026-6517

Mitre

CVSS v3.1

6.3

Medium

Base vector

AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:N/A:N

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

Fix

Insufficiently Protected Credentials

Weakness Enumeration

CWE-522

Related Identifiers

CVE-2026-6517

Affected Products

Mattermost

References · 2

• https://nvd.nist.gov/vuln/detail/CVE-2026-6517 · Security Note
• https://mattermost.com/security-updates · Vendor Advisory