7.7

CVE-2026-6517: mattermost Insufficiently Protected Credentials

CVSS: 7.7v3.1HighAnalyzed
Published 15-06-2026Last modified 15-06-2026
Open JSON

Vulnerability summary

CVE-2026-6517 is a high (CVSS 7.7) Insufficiently Protected Credentials vulnerability in mattermost. EPSS estimates a 0.32% chance of exploitation in the next 30 days, higher than 23.2% of scored vulnerabilities.

Overall risk
31/100
0100
Medium · default modelHow is this calculated?
CVSS score
7.7/10
010
High · v3.1 (NVD)
EPSS score
0.32%
0%100%
Low · +0.13 pp in 30 days
KEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded

Timeline

  1. 15-06-2026
    PublishedVulnerability first disclosed.
  2. 15-06-2026
    Last modifiedVulnerability information updated.

Description

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

CVSS metrics

2 scores · 2 sources · 1 version

EPSS trend

Probability

0.32%

Chance of exploitation in the next 30 days

Percentile

23%

Versus all other CVEs

30-day change

+0.13 pp

From 0.19% on 21-09-2026

21-09-202621-10-2026
EPSS score
0.32%

Known exploited

Compare KEV catalogs

Not in any of the 3 tracked catalogs.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Mattermost2 products

1 vendor · 2 products

References

1 links