All vulnerabilities
CVE-2026-18795

Mattermost: Missing server side validation allowed user to quarantine a DM and GM post

Mattermost MattermostApplications & CMS
Open in ThreatlineRecord JSON
CVSS
6.4Medium
ExploitationNo known exploitationNot in CISA KEV, which does not prove it is unexploitedCISA KEV
Exploit odds (EPSS)0.15%Chance of exploitation activity in the next 30 days, higher than 3% of CVEs. Scored 23 Oct 2026FIRST EPSS
Fixed inNone listedNo source names a fixed version. Check the vendor advisory below
Published16 Oct 2026Updated 16 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 11.10.x <= 11.10.0, 11.7.x <= 11.7.9, 11.9.x <= 11.9.1, 11.8.x <= 11.8.5 fail to enforce DM/GM check on server side which allows an authenticated user to quarantine a post belonging to DM or GM via direct API call.. Mattermost Advisory ID: MMSA-2026-00756

Text from CVE List

Affected versions 9

  • Mattermostaffected: 11.10.0 through 11.10.0CVE List
  • Mattermostaffected: 11.7.0 through 11.7.9CVE List
  • Mattermostaffected: 11.9.0 through 11.9.1CVE List
  • Mattermostaffected: 11.8.0 through 11.8.5CVE List
  • Mattermostunaffected: 11.11.0CVE List
  • Mattermostunaffected: 11.10.1CVE List
  • Mattermostunaffected: 11.7.10CVE List
  • Mattermostunaffected: 11.9.2CVE List
  • Mattermostunaffected: 11.8.6CVE List

References 1