CVE-2026-6343: mattermost server Auth Bypass — Fix

Description

Mattermost versions 11.5.x <= 11.5.1, 10.11.x <= 10.11.13, 11.4.x <= 11.4.3 fail to check public/private permissions which allows members without these permissions to access public playbooks via /get.. Mattermost Advisory ID: MMSA-2026-00591

Is your site exposed to CVE-2026-6343?

Run a free security scan — no signup, results in seconds.

CVSS v3.1 Score

4.3

MEDIUM

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

EPSS — Exploit Prediction

0.0017

Probability of exploitation

0.06%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-863 Incorrect Authorization

Affected Products

Vendor	Product	Versions
mattermost	mattermost_server	10.11.0 — 10.11.14
mattermost	mattermost_server	11.4.0 — 11.4.4
mattermost	mattermost_server	11.5.0 — 11.5.2

References

Advisories & Patches

https://mattermost.com/security-updates

Frequently Asked Questions

What is CVE-2026-6343? +

Mattermost versions 11.5.x <= 11.5.1, 10.11.x <= 10.11.13, 11.4.x <= 11.4.3 fail to check public/private permissions which allows members without these permissions to access public playbooks via /get.. Mattermost Advisory ID: MMSA-2026-00591 It has a CVSS v3.1 base score of 4.3 (MEDIUM).

How severe is CVE-2026-6343? +

CVE-2026-6343 has a CVSS v3.1 score of 4.3 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance. The EPSS score is 0.0017, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-6343? +

CVE-2026-6343 affects products from mattermost, specifically: mattermost_server. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-6343? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

Related Vulnerabilities

CVE-2026-50008

Parse Server is an open source backend that can be deployed to any infrastructure that can run Node.js. From version …

CVE-2026-42571

Pelican is a platform for creating data federations. From versions 7.21.0 to before 7.21.5, 7.22.0 to before 7.22.3, 7.23.0 to …

CVE-2026-42137

Kirby is an open-source content management system. Prior to versions 4.9.0 and 5.4.0, `pages.access/list` and `files.access/list` permissions are not consistently …

CVE-2026-54358

An incorrect authorization vulnerability in MISP allows an organization administrator to target site administrator accounts belonging to the same organization …

CVE-2026-42160

Data Space Portal is an open-source Software as a Service (SaaS) solution designed to streamline Dataspace management. From version 2.1.1 …

CVE-2026-42604

Actual is a local-first personal finance tool. The `POST /openid/config` endpoint in Actual Budget's sync-server versions <= 26.4.0 exposes the …

CVE-2026-6343