IRONSMITHINTEL
CRITICAL
|Auth: varies by cve|Reboot: required|Est. 30–60 minutes including reboot|Manual only

KB5008212: Windows Server 2022 Cumulative Update (December 2021)

The December 2021 Patch Tuesday cumulative update for Windows Server 2022 addresses 67 security vulnerabilities. Released during the Log4Shell crisis, this update also includes Windows Defender signature updates and remote code execution fixes.

Published Dec 14, 2021 · Updated May 10, 2026
Why patchRisk explained in plain English
Worst-case scenarioIf unpatched

Unpatched Windows Server 2022 systems after December 2021 are exposed to multiple privilege escalation and remote code execution vulnerabilities. Several December 2021 patches address flaws in Windows Remote Desktop and Active Directory that attackers can chain for unauthenticated domain compromise.

How the attack works

KB5008212 is the December 2021 monthly rollup for Windows Server 2022, addressing 67 CVEs across the Windows kernel, NTFS, Remote Desktop, Active Directory, and network services. December 2021 was an unusually high-risk patch cycle coinciding with Log4Shell discovery.

Am I affected?Quick check

Probably yes if any of these apply:

All Windows Server 2022 systems
Running Windows Server 2022 prior to KB5008212

Affected OS versions

Windows Server 2022
Fixed inKB5008212
Real-world incidentsWhat we've seen

A security team managing a large Windows Server 2022 deployment delays December 2021 patching due to Log4Shell remediation consuming all bandwidth. Three weeks into January 2022, a threat actor exploits a December 2021 Active Directory vulnerability on an internet-facing server to gain initial access. The unpatched NTFS driver vulnerability allows privilege escalation to SYSTEM within minutes.

How to patch

Manual download

For air-gapped servers or out-of-band deployment. Microsoft Update Catalog returns every OS-version variant of this update.

↗ Microsoft Update CatalogKB5008212

Manual remediation steps

30–60 minutes including reboot

Check if KB5008212 is Installed

Get-HotFix -Id KB5008212

Apply via Windows Update

# Check available updates
(New-Object -ComObject Microsoft.Update.Session).CreateUpdateSearcher().Search('IsInstalled=0').Updates | Select-Object Title

Apply Manually

1
Download KB5008212 from https://catalog.update.microsoft.com
2
Run the MSU installer as Administrator
3
Restart the server

Verify

Get-HotFix -Id KB5008212
[System.Environment]::OSVersion.Version
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