Detections
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Mattermost Server 10.11.x < 10.11.13 Improper Validation (MMSA-2026-00603)

low Nessus Plugin ID 310111

Synopsis

The remote host is affected by an improper validation vulnerability.

Description

The version of Mattermost Server installed on the remote host is affected by a vulnerability as referenced in the MMSA-2026-00603 advisory.

 - Mattermost versions 10.11.x prior to 10.11.13 fail to validate whether users were correctly owned by the correct Connected Workspace which allows a malicious remote server connected using the Connected Workspaces feature to change the displayed status of local users via the Connected Workspaces API.
 Mattermost Advisory ID: MMSA-2026-00603. (CVE-2026-27769)

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 10.11.13, 11.3.0 or later.

See Also

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

Plugin Details

Severity: Low

ID: 310111

File Name: mattermost_server_MMSA-2026-00603.nasl

Version: 1.1

Type: Remote

Family: CGI abuses

Published: 4/24/2026

Updated: 4/24/2026

Supported Sensors: Nessus

Risk Information

VPR

Risk Factor: Low

Score: 2.9

CVSS v2

Risk Factor: Low

Base Score: 3.3

Temporal Score: 2.4

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

CVSS Score Source: CVE-2026-27769

CVSS v3

Risk Factor: Low

Base Score: 2.7

Temporal Score: 2.4

Vector: CVSS:3.0/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:L/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: 3/16/2026

Vulnerability Publication Date: 4/15/2026

Reference Information

CVE: CVE-2026-27769

IAVA: 2026-A-0365