CVE-2026-10556
EUVD-2026-7737914.09.2026, 11:17
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-2026-00693EnginsightAffected Products (NVD)
| Vendor | Product | Version |
|---|---|---|
| mattermost | mattermost_server | 10.11.0 ≤ 𝑥 < 10.11.23 |
| mattermost | mattermost_server | 11.7.0 ≤ 𝑥 < 11.7.8 |
| mattermost | mattermost_server | 11.8.0 ≤ 𝑥 < 11.8.5 |
| mattermost | mattermost_server | 11.9.0 ≤ 𝑥 < 11.9.1 |
𝑥
= Vulnerable software versions
Early Detection
Affected products identified ahead of NVD analysis through intelligence sources
(CNA/ADP records, vendor advisories, Enginsight analysis).
| Vendor | Product | Version | Source |
|---|---|---|---|
| mattermost | mattermost | 11.9.0 | CNA |
| mattermost | mattermost | 11.8.0 ≤ 𝑥 ≤ 11.8.4 | CNA |
| mattermost | mattermost | 11.7.0 ≤ 𝑥 ≤ 11.7.7 | CNA |
| mattermost | mattermost | 10.11.0 ≤ 𝑥 ≤ 10.11.22 | CNA |
Common Weakness Enumeration
- CWE-754 - Improper Check for Unusual or Exceptional ConditionsThe software does not check or incorrectly checks for unusual or exceptional conditions that are not expected to occur frequently during day to day operation of the software.
- CWE-476 - NULL Pointer DereferenceA NULL pointer dereference occurs when the application dereferences a pointer that it expects to be valid, but is NULL, typically causing a crash or exit.
References