Deserialization of Untrusted Data in Microsoft products - CVE-2026-21511
Published: February 10, 2026
Vulnerability identifier: #VU122587
CSH Severity: Medium
CVSS v4: 8.7 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-21511
CWE-ID: CWE-502
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to compromise the target system.
The vulnerability exists due to insecure input validation when processing serialized data in Microsoft Outlook. A remote attacker can pass specially crafted data to the application and gain access to sensitive information.
Affected software
Microsoft SharePoint Server Subscription Edition
Microsoft SharePoint Enterprise Server
Microsoft SharePoint Server
Microsoft 365 Apps for Enterprise
Microsoft Word
Microsoft Office
Microsoft Office LTSC
Microsoft SharePoint Enterprise Server
Microsoft SharePoint Server
Microsoft 365 Apps for Enterprise
Microsoft Word
Microsoft Office
Microsoft Office LTSC
How to mitigate CVE-2026-21511
Install updates from vendor's website.