SB2026011440 - Remote code execution in Microsoft Windows Server Update Service (WSUS)
Published: January 14, 2026
Security Bulletin ID
SB2026011440
Severity
High
Patch available
YES
Number of vulnerabilities
1
Exploitation vector
Remote access
Highest impact
Code execution
Breakdown by Severity
- Low
- Medium
- High
- Critical
Description
This security bulletin contains information about 1 security vulnerability.
1) Input validation error (CVE-ID: CVE-2026-20856)
The vulnerability allows a remote attacker to execute arbitrary code on the target system.
The vulnerability exists due to insufficient validation of user-supplied input in Windows Server Update Service (WSUS). A remote attacker can perform a man-in-the-middle (MitM) attack and execute arbitrary code on the system.
Remediation
Install update from vendor's website.