Detections
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Mattermost Server 10.11.x <= 10.11.9 / 11.0.x <= 11.2.x Improper Access Control (MMSA-2025-00549)

low Nessus Plugin ID 299394

Synopsis

The remote host is missing a security update.

Description

The version of Mattermost Server installed on the remote host is affected by a vulnerability as referenced in the MMSA-2025-00549 advisory.

 - Mattermost versions 10.11.x <= 10.11.9 and 11.0.x <= 11.2.x fail to properly enforce access control checks in the common teams API. This allows the API to return team information to users who were deactivated between the initial authorization check and data retrieval, resulting in information disclosure. (CVE-2026-20796)

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

Solution

Upgrade to Mattermost Server version 10.11.10, 11.3.0 or later.

See Also

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

Plugin Details

Severity: Low

ID: 299394

File Name: mattermost_server_MMSA-2025-00549.nasl

Version: 1.2

Type: remote

Family: CGI abuses

Published: 2/18/2026

Updated: 2/19/2026

Supported Sensors: Nessus

Risk Information

VPR

Risk Factor: Low

Score: 2.9

CVSS v2

Risk Factor: Low

Base Score: 2.1

Temporal Score: 1.6

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

CVSS Score Source: CVE-2026-20796

CVSS v3

Risk Factor: Low

Base Score: 3.1

Temporal Score: 2.7

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

Temporal Vector: CVSS:3.0/E:U/RL:O/RC:C

Vulnerability Information

CPE: cpe:/a:mattermost:mattermost_server

Required KB Items: installed_sw/Mattermost Server

Exploit Ease: No known exploits are available

Patch Publication Date: 1/15/2026

Vulnerability Publication Date: 1/15/2026

Reference Information

CVE: CVE-2026-20796