---
id: CVE-2026-93849
title: >-
  Mattermost allows authenticated users to trigger excessive memory allocation
  via crafted msgpack binary WebSocket frames
summary: >-
  Mattermost versions 11.9.x <= 11.9.1, 11.8.x <= 11.8.5, 11.7.x <= 11.7.10,
  11.10.x <= 11.10.1 Mattermost fail to apply allocation limits to the
  byte-string decode paths in its WebSocket msgpack decoder, which allows an
  authenticated remo…
severity: medium
cvss: 6.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H'
cvssSource: cna
cwe:
  - CWE-789
vendor: Mattermost
product: Mattermost
affected:
  - Mattermost >= 11.9.0 <= 11.9.1
  - Mattermost >= 11.8.0 <= 11.8.5
  - Mattermost >= 11.7.0 <= 11.7.10
  - Mattermost >= 11.10.0 <= 11.10.1
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-10-26T15:32:42.705205Z'
published: '2026-10-26'
updated: '2026-10-26'
sourceUpdated: '2026-10-26T16:46:45.736Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-93849'
references:
  - url: 'https://mattermost.com/security-updates'
    label: MMSA-2026-00768
tags:
  - cve.org
ingestedAt: '2026-10-26T15:29:30.533Z'
---

## Overview

Mattermost versions 11.9.x <= 11.9.1, 11.8.x <= 11.8.5, 11.7.x <= 11.7.10, 11.10.x <= 11.10.1 Mattermost fail to apply allocation limits to the byte-string decode paths in its WebSocket msgpack decoder, which allows an authenticated remote attacker to cause excessive server memory allocation via a crafted binary WebSocket frame declaring a Bin32 payload length of up to 4,294,967,295 bytes.. Mattermost Advisory ID: MMSA-2026-00768

## Affected

- `Mattermost >= 11.9.0 <= 11.9.1`
- `Mattermost >= 11.8.0 <= 11.8.5`
- `Mattermost >= 11.7.0 <= 11.7.10`
- `Mattermost >= 11.10.0 <= 11.10.1`

## Remediation

Update Mattermost to versions 11.11.0, 11.9.2, 11.8.6, 11.7.11, 11.10.2 or higher.