Detections
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Mattermost Server 10.11.x < 10.11.22 / 11.7.x < 11.7.7 Multiple Vulnerabilities (MMSA-2026-00672, MMSA-2026-00675, MMSA-2026-00704)

medium Nessus Plugin ID 338331

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Synopsis

The remote host is affected by multiple vulnerabilities.

Description

The version of Mattermost Server installed on the remote host is affected by multiple vulnerabilities as referenced in the MMSA-2026-00672, MMSA-2026-00675, MMSA-2026-00704 advisories.

 - Mattermost versions 11.7.x <= 11.7.6, 10.11.x <= 10.11.21 fail to prevent guest users from receiving Board Admin privileges during board archive import which allows a board member to escalate a guest user to Board Admin via importing a crafted .boardarchive file. Mattermost Advisory ID:
 MMSA-2026-00672. (CVE-2026-16044)

 - Mattermost versions 11.7.x <= 11.7.6, 10.11.x <= 10.11.21 Mattermost failed to restrict OAuth deauthorization and personal access token management endpoints to direct user sessions, which allowed an OAuth app with a delegated user token to revoke the user's authorizations or tokens for other integrations via account-management endpoints. Mattermost Advisory ID: MMSA-2026-00704.
 (CVE-2026-16045)

 - Mattermost versions 11.7.x <= 11.7.6, 10.11.x <= 10.11.21 fail to enforce run-state validation on write operations for finished playbook runs which allows a run participant to modify status, checklists, retrospective content, ownership, and participants on completed runs via REST and GraphQL API requests. Mattermost Advisory ID: MMSA-2026-00675. (CVE-2026-16046)

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

Solution

Upgrade to Mattermost Server version 10.11.22, 11.7.7, 11.9.0 or later.

See Also

https://mattermost.com/security-updates/

Plugin Details

Severity: Medium

ID: 338331

File Name: mattermost_server_MMSA-2026-00672_00675_00704.nasl

Version: 1.1

Type: Remote

Family: CGI abuses

Published: 8/20/2026

Updated: 8/20/2026

Supported Sensors: Nessus

Risk Information

VPR

Risk Factor: Low

Score: 2.1

Percentile: 7.91

CVSS v2

Risk Factor: Medium

Base Score: 5.5

Vector: CVSS2#AV:N/AC:L/Au:S/C:N/I:P/A:P

CVSS Score Source: CVE-2026-16044

CVSS v3

Risk Factor: Medium

Base Score: 5.4

Vector: CVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L

Vulnerability Information

CPE: cpe:/a:mattermost:mattermost_server

Required KB Items: installed_sw/Mattermost Server

Patch Publication Date: 7/17/2026

Vulnerability Publication Date: 8/17/2026

Reference Information

CVE: CVE-2026-16044, CVE-2026-16045, CVE-2026-16046