Home/CVE/Improper input validation in Windows Server Update Service allows an unauthorized attacker to execute code over a networ
CVE

CVE-2026-20856

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

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

HIGH · CVSS 8.1 EPSS 0.00184
Schedule remediation
  • CVSS base score ≥ 7.0
Sigma rules0 YARA rules0
⬡

Weakness Classification

CWE-20Improper Input Validation
▤

Affected Products & Versions

13
microsoft windows 10 1607< 10.0.14393.8783
microsoft windows 10 1809< 10.0.17763.8276
microsoft windows 10 21h2< 10.0.19044.6809
microsoft windows 10 22h2< 10.0.19045.6809
microsoft windows 11 23h2< 10.0.22631.6491
microsoft windows 11 24h2< 10.0.26100.7623
microsoft windows 11 25h2< 10.0.26200.7623
microsoft windows server 2012all versions
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Scoring & Timeline

8.1
HIGH · CVSS v3.1 · secure@microsoft.com
View on NVD
Attack Vector
Network Adjacent Local Physical
Attack Complexity
Low High
Privileges Required
None Low High
User Interaction
None Required
Scope
Unchanged Changed
Confidentiality
None Low High
Integrity
None Low High
Availability
None Low High
Published to NVD13 Jan 2026 · 06:16 PM
CVSS VectorCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
SSVC triage · cisa-vulnrichment
Exploitation
none
Automatable
no
Technical impact
total
SSVC asks the questions that actually drive patch urgency: is it being exploited, can attacks be automated, and how total is the impact.
⚑

Vendor Advisories

1
msrcCVE-2026-20856Remote Code Execution
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