All vulnerabilities
CVE-2026-19541

Mattermost: Outgoing OAuth connection client secret exposure during connection validation

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)0.22%Chance of exploitation activity in the next 30 days, higher than 11% 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 11.9.x <= 11.9.1, 11.8.x <= 11.8.5, 11.7.x <= 11.7.10, 11.10.x <= 11.10.1 fail to require re-entry of the stored client secret when validating an outgoing OAuth connection, which allows an authenticated user with permission to manage outgoing OAuth connections to obtain the secret via pointing the token URL at an attacker-controlled endpoint and triggering validation.. Mattermost Advisory ID: MMSA-2026-00761

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