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VULNERABILITIES

CVE-2026-5740 Details

Description

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

Metrics

CVSS 3.x Severity and Vector Strings:

CNA: [email protected]CVSS-B:7.5 HIGHVector:CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

References to Advisories, Solutions, and Tools

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URLSource(s)Tag(s)
https://mattermost.com/security-updates [email protected]Vendor Advisory

Weakness Enumeration

CWE-IDCWE NameSource
CWE-789Memory Allocation with Excessive Size Value[email protected]

Affected Products

ProductVersions
mattermost mattermost server
>= 10.11.0, < 10.11.15
>= 11.4.0, < 11.4.5
>= 11.5.0, < 11.5.4
>= 11.6.0, < 11.6.1

CPE

  • cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*

Remediation

  • No remediation found in references.

Change History

5 change records found show changes

QUICK INFO

CVE Dictionary Entry:
CVE-2026-5740
NVD Published Date:
May 22, 2026
NVD Last Modified:
Jul 23, 2026
Source:
[email protected]
CVE-2026-5740 Details - Not Deferred