Medium severity5.3NVD Advisory· Published Sep 14, 2026· Updated Sep 14, 2026
CVE-2026-10556
CVE-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
AI Insight
LLM-synthesized narrative grounded in this CVE's description and references.
Affected products
2- Range: <=11.9.0, <=11.8.4, <=11.7.7, <=10.11.22
- Range: <=11.9.0, <=11.8.4, <=11.7.7, <=10.11.22
Patches
Vulnerability mechanics
References
1News mentions
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