CVE-2026-10556
5.3
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Summary
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
Affected Software
| Vendor | Product | Version Range | Status |
|---|---|---|---|
| Mattermost | Mattermost | 11.9.0 <= 11.9.0 | affected |
| Mattermost | Mattermost | 11.8.0 <= 11.8.4 | affected |
| Mattermost | Mattermost | 11.7.0 <= 11.7.7 | affected |
| Mattermost | Mattermost | 10.11.0 <= 10.11.22 | affected |
| Mattermost | Mattermost | 11.10.0 | unaffected |
| Mattermost | Mattermost | 11.9.1 | unaffected |
| Mattermost | Mattermost | 11.8.5 | unaffected |
| Mattermost | Mattermost | 11.7.8 | unaffected |
| Mattermost | Mattermost | 10.11.23 | unaffected |
Weaknesses
- CWE-754: CWE-754: Improper Check for Unusual or Exceptional Conditions
ADP Enrichment
CISA ADP Vulnrichment
- SSVC:
- Exploitation: none
- Automatable: yes
- Technical Impact: partial
References
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