Detections
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SCA: security update for github.com/mattermost/mattermost-server, github.com/mattermost/mattermost/server/v8 (GHSA-w9m8-p4cc-4qj9)

high Tenable Self-Hosted Container Security Plugin ID 444128

Description

There are packages installed that are affected by a vulnerability referenced in the following CVE:

 - Mattermost versions 11.6.x <= 11.6.0, 11.5.x <= 11.5.3, 11.4.x <= 11.4.4, 10.11.x <= 10.11.14 fail to
 properly validate msgpack-encoded WebSocket frames before memory allocation which allows an
 unauthenticated remote attacker to crash the server process and cause a full service outage for all users
 via a crafted binary WebSocket message sent to the public WebSocket endpoint.. Mattermost Advisory ID:
 MMSA-2026-00647 (CVE-2026-5740)

Solution

Update the github.com/mattermost/mattermost-server library and its related packages to version 10.11.15 or later.

See Also

https://github.com/advisories/GHSA-w9m8-p4cc-4qj9

Plugin Details

Severity: High

ID: 444128

Version: Revision 1.1

Type: Local

Family: SCA Checks

Published: 6/30/2026

Updated: 6/30/2026

Risk Information

VPR

Risk Factor: Low

Score: 3.6

Vendor

Vendor Severity: High

CVSS v2

Risk Factor: High

Base Score: 7.8

Temporal Score: 5.8

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

CVSS Score Source: CVE-2026-5740

CVSS v3

Risk Factor: High

Base Score: 7.5

Temporal Score: 6.5

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

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

Vulnerability Information

Exploit Ease: No known exploits are available

Patch Publication Date: 5/26/2026

Vulnerability Publication Date: 5/22/2026

Reference Information

CVE: CVE-2026-5740

cwe: CWE-789