CVE-2026-6342

Name: CVE-2026-6342
Creator: NVD / NIST
Published: 2026-05-18T08:16:14.717+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

MEDIUMCVSS 4.3/10EPSS 0.15%

Last modified Jun 17, 2026

CVE-2026-6342 is a medium-severity vulnerability rated 4.3/10 on the CVSS scale. Mattermost Plugins versions <=11.5 11.1.5 10.13.11 11.3.4.0 fail to appropriately check for valid namespaces which allows plugin users to create subscriptions to groups that were not whitelisted via creating groups that share the same prefix as a whitelisted group. Mattermost Advisory ID: MMSA-2026-00601. EPSS estimates a 0.15% chance of exploitation in the next 30 days.

Description

Mattermost Plugins versions <=11.5 11.1.5 10.13.11 11.3.4.0 fail to appropriately check for valid namespaces which allows plugin users to create subscriptions to groups that were not whitelisted via creating groups that share the same prefix as a whitelisted group. Mattermost Advisory ID: MMSA-2026-00601

Metrics

CVSS 3.1

4.3/10

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

EPSS Probability

0.15%

4.7th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-863

Affected Software

Vendor	Product	Versions
Mattermost	Mattermost Server	>= 10.13.0, <= 10.13.11
Mattermost	Mattermost Server	>= 11.1.0, <= 11.1.5
Mattermost	Mattermost Server	>= 11.3.0, <= 11.3.4

References

https://mattermost.com/security-updatesVendor Advisory

Timeline

Published: May 18, 2026
Last Modified: Jun 17, 2026
Status: Analyzed

Frequently Asked Questions

What is CVE-2026-6342?

How severe is CVE-2026-6342?

CVE-2026-6342 has a CVSS score of 4.3/10 (MEDIUM severity). The EPSS model estimates a 0.15% probability of exploitation in the next 30 days.

How do I fix CVE-2026-6342?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2026-6342?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST