CVE-2026-9812

Medium

Description

Mattermost versions 11.9.x <= 11.9.0, 11.8.x <= 11.8.4, 11.7.x <= 11.7.7, 10.11.x <= 10.11.22 fail to validate that a property field belongs to the specified run before updating its value which allows an authenticated user with run property-management access to crash the Playbooks plugin via a REST request referencing a property field that belongs to a different run. Mattermost Advisory ID: MMSA-2026-00684

SeverityMedium

CVSS6.5

Exploit probability—

Product

Mattermost Server

PublishedSep 14, 2026

First seenSep 14, 2026

Weakness typeCWE-639Authorization bypass through user-controlled key

How to fix

Update

mattermost mattermost_server10.11.23, 11.7.8, 11.8.5, 11.9.1 or later

Vendor advisories

mattermost.com/security-updates

Affected products

Product	Affected versions	Fixed in
mattermost mattermost_server	10.11.0 ≤ v < 10.11.23, 11.7.0 ≤ v < 11.7.8, 11.8.0 ≤ v < 11.8.5, 11.9.0 ≤ v < 11.9.1	10.11.23, 11.7.8, 11.8.5, 11.9.1

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