CVE-2026-20856
HighCVSS 8.1Exploitation Probability (EPSS)
Elevated risk62th percentile - higher than 62% of all known CVEs
Summary
Improper input validation in Windows Server Update Service allows an unauthorized attacker to execute code over a network.
Risk Assessment
An attacker can remotely execute malicious code on the server, leading to full system compromise and potential lateral movement.
Recommendation
Install the latest Windows security updates from Microsoft.
Other vulnerabilities in Windows Server Update Service
See all- CVE-2026-83499High
Insufficient granularity of access control in Windows Server Update Service allows an authorized attacker to elevate privileges locally.
- CVE-2026-81969High
Insufficient granularity of access control in Windows Server Update Service allows an authorized attacker to elevate privileges locally.
- CVE-2026-105009High
Incorrect default permissions in Windows Server Update Service allows an authorized attacker to elevate privileges locally.
- CVE-2025-59287CriticalActively exploited
Deserialization of untrusted data in Windows Server Update Service allows an unauthorized attacker to execute code over a network.
- CVE-2026-50444High
Missing authentication for a critical function in Windows Server Update Service (WSUS) allows an authorized attacker to elevate privileges over a network.
- CVE-2026-50328High
An unhandled exception in Windows Server Update Service (WSUS) allows an unauthorized attacker to perform tampering over a network. This vulnerability could compromise the integrity of updates.
Original NVD description (English source)
Improper input validation in Windows Server Update Service allows an unauthorized attacker to execute code over a network.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS