Vulnerability · Published Jan 13, 2026 · Assigned by microsoft
CVE-2026-20856Windows Server Update Service (WSUS) Remote Code Execution Vulnerability
High 8.1
In plain English
A high-severity improper input validation in Windows 10 Version 1607 from Microsoft. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 1.1% (higher than 66% of all known vulnerabilities).
Severity (CVSS 3.1)8.1High
Exploit odds (30 days)1.1%top 33.8% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known
Official description
Improper input validation in Windows Server Update Service allows an unauthorized attacker to execute code over a network.
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| Microsoft | Windows 10 Version 1607 | 10.0.14393.0 – before 10.0.14393.8783 |
| Microsoft | Windows 10 Version 1809 | 10.0.17763.0 – before 10.0.17763.8276 |
| Microsoft | Windows 10 Version 21H2 | 10.0.19044.0 – before 10.0.19044.6809 |
| Microsoft | Windows 10 Version 22H2 | 10.0.19045.0 – before 10.0.19045.6809 |
| Microsoft | Windows 11 version 23H2 | 10.0.22631.0 – before 10.0.22631.6491 |
| Microsoft | Windows 11 Version 23H2 | 10.0.22631.0 – before 10.0.22631.6491 |
| Microsoft | Windows 11 Version 24H2 | 10.0.26100.0 – before 10.0.26100.7623 |
| Microsoft | Windows 11 Version 25H2 | 10.0.26200.0 – before 10.0.26200.7623 |
| Microsoft | Windows Server 2012 | 6.2.9200.0 – before 6.2.9200.25868 |
| Microsoft | Windows Server 2012 (Server Core installation) | 6.2.9200.0 – before 6.2.9200.25868 |
| Microsoft | Windows Server 2012 R2 | 6.3.9600.0 – before 6.3.9600.22968 |
| Microsoft | Windows Server 2012 R2 (Server Core installation) | 6.3.9600.0 – before 6.3.9600.22968 |
| Microsoft | Windows Server 2016 | 10.0.14393.0 – before 10.0.14393.8783 |
| Microsoft | Windows Server 2016 (Server Core installation) | 10.0.14393.0 – before 10.0.14393.8783 |
| Microsoft | Windows Server 2019 | 10.0.17763.0 – before 10.0.17763.8276 |
| Microsoft | Windows Server 2019 (Server Core installation) | 10.0.17763.0 – before 10.0.17763.8276 |
| Microsoft | Windows Server 2022 | 10.0.20348.0 – before 10.0.20348.4648 |
| Microsoft | Windows Server 2022, 23H2 Edition (Server Core installation) | 10.0.25398.0 – before 10.0.25398.2092 |
| Microsoft | Windows Server 2025 | 10.0.26100.0 – before 10.0.26100.32230 |
| Microsoft | Windows Server 2025 (Server Core installation) | 10.0.26100.0 – before 10.0.26100.32230 |
Weakness: CWE-20 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C
References
- Windows Server Update Service (WSUS) Remote Code Execution Vulnerability vendor-advisory, patch