CVE-2026-20856

Severity CVSS v4.0:

Pending analysis

Type:

CWE-20 Input Validation

Publication date:

13/01/2026

Last modified:

13/01/2026

Description

Improper input validation in Windows Server Update Service allows an unauthorized attacker to execute code over a network.

Impact

Vector 3.x

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H CVSS v3.1 Severity and Metrics:

Base Score: 8.10 HIGH
Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

Attack Vector (AV): Network
Attack Complexity (AC): High
Privileges Required (PR): None
User Interaction (UI): None
Scope (S): Unchanged
Confidentiality (C): High
Integrity (I): High
Availability (A): High

Base Score 3.x

8.10

Severity 3.x

HIGH

References to Advisories, Solutions, and Tools

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-20856