Is CVE-2026-6345 in the CISA KEV catalog?

No. CVE-2026-6345 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2026-6345?

CVE-2026-6345 has a CVSS v3 base score of 6.5 (MEDIUM).

What is the EPSS score for CVE-2026-6345?

CVE-2026-6345 has an EPSS score of 0.23% (14th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2026-6345?

Upgrade mattermost server to 11.5.2 or later.

CVE & CISA-KEV Catalog

CVE-2026-6345

MEDIUM

6.5

CVSS v3

NVD

Description

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

CWE-522

How to fix

Remediation Available

mattermost serverNVD

Affected:>= 11.5.0, < 11.5.2Fixed in:11.5.2CVE-2026-6345derived from NVD

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredHigh

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityHigh

IntegrityHigh

AvailabilityNone

CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:N

Exploit Intelligence

0.23%probability of exploitation in 30 days

14thpercentile

Low risk: more likely to be exploited than 14% of all known CVEs.

References

Vendor Advisory1

mattermost.com

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-05-18.