CVE-2026-5740

HIGH EPSS 24.5%
Published May 22, 20261mo ago · Modified Jun 17, 20261w ago
7.5 CVSS 3.1
High
Find Similar
Published May 22, 2026 1mo ago
Last Modified Jun 17, 2026 1w ago

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

CVSS Details

Base Score
7.5
Exploitability
3.9
Impact
3.6
Vector string
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Attack Vector Network
Attack Complexity Low
Privileges Required None
User Interaction None
Scope Unchanged
Confidentiality None
Integrity None
Availability High

Threat Intelligence

EPSS Exploit Probability
24.5% percentile
Exploit & Patch Status
No Known Exploit
No Patch Available

Weaknesses 1

CWE-789

Affected Products 4

VendorProductVersionRange
mattermostmattermost_server*≥10.11.0  –  <10.11.15
mattermostmattermost_server*≥11.4.0  –  <11.4.5
mattermostmattermost_server*≥11.5.0  –  <11.5.4
mattermostmattermost_server*≥11.6.0  –  <11.6.1

References 1

  • mattermost.com https://mattermost.com/security-updates
    Vendor Advisory

Remediation

No remediation data recorded yet

Check vendor advisories and the NVD entry for patch availability.