What is CVE-2026-6345?

CVE-2026-6345 is a medium-severity vulnerability in Mattermost, classified under Insufficiently Protected Credentials. CVSS score: 6.5/10. Published 2026-05-18.

How severe is CVE-2026-6345?

Medium severity. CVSS v3 base score is 6.5 out of 10.

Vulnerability in Mattermost

CVE-2026-6345

Mattermost versions 11.5.x <= 11.5.1, 10.11.x <= 10.11.13, 11.4.x <= 11.4.3 fail prevent disclosure of created user password which allows a malicious attacker to impersonate a user via the use of some of those passwords.. Mattermost Advisory ID: MMSA-2026-00614

Published 2026-05-18 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:N.

EPSS exploit prediction

EPSS: 0.004 (31.0th percentile), scored 2026-09-30.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 31st percentile — 31.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.002 · newest: 0.004 · change: +0.002

Affected products

Mattermost — versions 11.5.0, 10.11.0, 11.4.0
Mattermost Server

Weakness classification (CWE)

CWE-522 — Insufficiently Protected Credentials

References

mattermost.com/security-updates (vendor-advisory, Vendor Advisory)

Frequently asked questions

What is CVE-2026-6345?: CVE-2026-6345 is a medium-severity vulnerability in Mattermost, classified under Insufficiently Protected Credentials. CVSS score: 6.5/10. Published 2026-05-18.
How severe is CVE-2026-6345?: Medium severity. CVSS v3 base score is 6.5 out of 10.