All vulnerabilities
CVE-2026-93849

Mattermost allows authenticated users to trigger excessive memory allocation via crafted msgpack binary WebSocket frames

Mattermost MattermostApplications & CMS
Open in ThreatlineRecord JSON
CVSS
6.5Medium
ExploitationNo known exploitationNot in CISA KEV, which does not prove it is unexploitedCISA KEV
Exploit odds (EPSS)No scoreNo FIRST EPSS score in this snapshot yet
Fixed inNone listedNo source names a fixed version. Check the vendor advisory below
Published26 Oct 2026Updated 26 Oct 2026CVE List

What fixes it

No source in this snapshot names a fixed version. The vendor advisories under References are the place to check.

Description

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

Text from CVE List

Affected versions 9

  • Mattermostaffected: 11.9.0 through 11.9.1CVE List
  • Mattermostaffected: 11.8.0 through 11.8.5CVE List
  • Mattermostaffected: 11.7.0 through 11.7.10CVE List
  • Mattermostaffected: 11.10.0 through 11.10.1CVE List
  • Mattermostunaffected: 11.11.0CVE List
  • Mattermostunaffected: 11.9.2CVE List
  • Mattermostunaffected: 11.8.6CVE List
  • Mattermostunaffected: 11.7.11CVE List
  • Mattermostunaffected: 11.10.2CVE List

References 1