Mattermost <11.10: Unenforced DM/GM Quarantine API (CVE-2026-18795)
CVE-2026-18795 Published on October 16, 2026

Missing server side validation allowed user to quarantine a DM and GM post
Mattermost versions 11.10.x <= 11.10.0, 11.7.x <= 11.7.9, 11.9.x <= 11.9.1, 11.8.x <= 11.8.5 fail to enforce DM/GM check on server side which allows an authenticated user to quarantine a post belonging to DM or GM via direct API call.. Mattermost Advisory ID: MMSA-2026-00756

Vendor Advisory NVD

Vulnerability Analysis

CVE-2026-18795 can be exploited with network access, and requires small amount of user privileges. This vulnerability is consided to have a high level of attack complexity. The potential impact of an exploit of this vulnerability is considered to have a high impact on confidentiality, with no impact on integrity and availability.

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

Weakness Type

What is an AuthZ Vulnerability?

The software does not perform an authorization check when an actor attempts to access a resource or perform an action.

CVE-2026-18795 has been classified to as an AuthZ vulnerability or weakness.


Products Associated with CVE-2026-18795

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Affected Versions

Mattermost: