VULNERABILITY INTELLIGENCE

CVE-2026-10556

CVSS score5.3 MEDIUM
EPSS probability0.42%
CISA KEVNot currently listed
Published2026-09-14
Last modified2026-10-07
CVSS vectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Description

Mattermost versions 11.9.x <= 11.9.0, 11.8.x <= 11.8.4, 11.7.x <= 11.7.7, 10.11.x <= 10.11.22 fail to validate null entries in Microsoft Graph webhook notification payloads, which allows an unauthenticated attacker to crash the Microsoft Calendar plugin process and deny calendar integration service to all users on the instance via a crafted {{POST}} request to the public webhook endpoint.. Mattermost Advisory ID: MMSA-2026-00693

Weakness classification

  • responsibledisclosure@mattermost.com: CWE-754
  • nvd@nist.gov: CWE-476

Primary references