Mattermost 11.9.x <= 11.9.0 Run Property Validation Flaw Crash Playbooks
CVE-2026-9812 Published on September 14, 2026

Missing property field ownership validation in Playbooks run property update endpoint
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

Vendor Advisory NVD

Vulnerability Analysis

CVE-2026-9812 is exploitable with network access, and requires small amount of user privileges. This vulnerability is considered to have a low attack complexity. The potential impact of an exploit of this vulnerability is considered to have no impact on confidentiality and integrity, and a high impact on availability.

Attack Vector:
NETWORK
Attack Complexity:
LOW
Privileges Required:
LOW
User Interaction:
NONE
Scope:
UNCHANGED
Confidentiality Impact:
NONE
Integrity Impact:
NONE
Availability Impact:
HIGH

Weakness Type

What is an Insecure Direct Object Reference / IDOR Vulnerability?

The system's authorization functionality does not prevent one user from gaining access to another user's data or record by modifying the key value identifying the data.

CVE-2026-9812 has been classified to as an Insecure Direct Object Reference / IDOR vulnerability or weakness.


Products Associated with CVE-2026-9812

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Affected Versions

Mattermost: