CVE-2026-10556EPSS p14.6%

CVE-2026-10556CVE-2026-10556

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

Scoring

CVSS 5.3 ()
VectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
EPSS0.25% probability of exploitation · percentile 14.6% · 2026-10-05T12:00:23Z
Last modified2026-09-16
Sourced from NVD + FIRST.org EPSS. Curated for EU compliance use cases by Adam Lundqvist, Founder at SQUR.