CVE-2026-6517 json
Mattermost Desktop App fails to restrict the allow list of domains which NTLM credentials are passed
published 2026-06-15 4 mo ago modified 2026-06-17 4 mo ago also EUVD-2026-36725
- cvss
- 6.3
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.2%
- EPSS 0.2% chance of exploitation in 30 days, percentile 8%
- public exploits
- 0
- none known
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
Patch / fix
- Mattermost Mattermost 5.13.6.0, 6.2.0
CISA SSVC
- Exploitation
- none
- Automatable
- no
- Technical impact
- partial
- Assessed
- 4 mo ago
Exploit prediction
0.19% chance of exploitation in the next 30 days, higher than 8% of all scored CVEs (FIRST EPSS, 2026-11-08).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 3.1 | 6.3 | CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:N/A:N |
| NVD | 3.1 | 7.7 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N |
Affected products
- Mattermost Mattermost
Classification
- Weakness
-
- CWE-522 Insufficiently Protected Credentials
References
-
mattermost.com
/security-updates
vendor-advisory
Sources
- CVE List CVE-2026-6517
- NVD CVE-2026-6517
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