Windows Runtime Remote Code Execution Vulnerability (CVE-2022-21971)
Published In CISA KEV since Sources: SingCERT, CVE.org
- Actively exploited
- Source: CSA/SingCERT How we classify
What is affected, what to do
Windows Runtime Remote Code Execution Vulnerability
The vulnerability is being actively exploited; treat it as a priority. Update Microsoft Windows 10 Version 1809 to version 10.0.17763.2565, Microsoft Windows Server 2019 to version 10.0.17763.2565, Microsoft Windows Server 2019 (Server Core installation) to version 10.0.17763.2565. Immediate actions, mitigation and detection rules are in the runbook below.
- Affected
- Microsoft Windows 10 Version 1809
lt 10.0.17763.0..10.0.17763.2565 - Microsoft Windows Server 2019
lt 10.0.17763.0..10.0.17763.2565 - Microsoft Windows Server 2019 (Server Core installation)
lt 10.0.17763.0..10.0.17763.2565 - Microsoft Windows 10 Version 1909
lt 10.0.0..10.0.18363.2094 - Microsoft Windows 10 Version 21H1
lt 10.0.0..10.0.19043.1526 - Microsoft Windows Server 2022
lt 10.0.20348.0..10.0.20348.524 - Microsoft Windows 10 Version 20H2
lt 10.0.0..10.0.19042.1526 - Microsoft Windows Server version 20H2
lt 10.0.0..10.0.19042.1526 - Microsoft Windows 11 version 21H2
lt 10.0.0..10.0.22000.493 - Microsoft Windows 10 Version 21H2
lt 10.0.19043.0..10.0.19044.1526
- Microsoft Windows 10 Version 1809
- Fixed in
- Microsoft Windows 10 Version 1809
10.0.17763.2565 - Microsoft Windows Server 2019
10.0.17763.2565 - Microsoft Windows Server 2019 (Server Core installation)
10.0.17763.2565 - Microsoft Windows 10 Version 1909
10.0.18363.2094 - Microsoft Windows 10 Version 21H1
10.0.19043.1526 - Microsoft Windows Server 2022
10.0.20348.524 - Microsoft Windows 10 Version 20H2
10.0.19042.1526 - Microsoft Windows Server version 20H2
10.0.19042.1526 - Microsoft Windows 11 version 21H2
10.0.22000.493 - Microsoft Windows 10 Version 21H2
10.0.19044.1526
- Microsoft Windows 10 Version 1809
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Metrics
7.8
Priority
XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.
Source: NVD, CVSS v3
7.8
CVSS v3
Severity High on the scale from 0 to 10.
Source: SingCERT, CVE.org
53.8 %
EPSS score
High — model estimates ≥ 50% chance of real-world exploitation within 30 days.
Source: FIRST EPSS, percentile 99.0
Show all metrics
- Severity
- Critical
Priority (0–325)
The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first?
Read in glossary- 217.82 Methodology
Exploit maturity
An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack.
Read in glossary- actively exploitedSource: CSA/SingCERT How we classify
XIEM Effective CVSS
XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command.
Read in glossary- 7.8 Methodology
CVSS v3
CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.
Read in glossary- 7.8
EPSS score
The EPSS score is the absolute model output for an individual vulnerability: the estimated probability of real-world exploitation within the next 30 days, expressed as a value between 0 and 1 (i.e. 0 % to 100 %). A score of 0.42 means „the model estimates a 42 % chance of real-world exploitation within 30 days“.
Read in glossary- 53.8 %
- High — model estimates ≥ 50% chance of real-world exploitation within 30 days.
EPSS percentile
The EPSS percentile is the relative position of a vulnerability within all EPSS-scored CVEs, expressed as a value between 0 and 1. A percentile of 0.90 means „this CVE has a higher EPSS score than 90 % of all other scored CVEs“. Unlike the EPSS score, it is not a probability — but a positioning within a ranking.
Read in glossary- 99.0
- Critical — this CVE ranks in the top fifth of all CVEs scored today (rank ≥ 80%).
KEV status
The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.
Read in glossary- Actively exploited
- Published
In CISA KEV since
The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.
Read in glossary
Response and mitigation
Why act now?
Prioritisation rationale
This Windows Runtime flaw gives code execution in the user's context as soon as a victim opens a crafted file. A public proof-of-concept has circulated since disclosure, which explains its KEV listing and very high exploitation likelihood. The natural use case is document-borne phishing against office workstations and shared terminal servers. CISA does not flag ransomware use, but the flaw is a solid initial-access primitive. Despite the local attack vector, treat it as high priority wherever users routinely open external Office attachments. The fix has been available since February 2022, so any remaining vulnerable host points mainly to a patch or lifecycle-management gap, which is relevant evidence under NIS2.
Runbook step 1
Immediate response (0-24 h)
- Deploy the February 2022 cumulative security update (or any later cumulative update) to all Windows clients and servers. Minimum safe builds: Windows 10 1809 / Server 2019 (incl. Server Core) 10.0.17763.2565, 1909 10.0.18363.2094, 20H2 10.0.19042.1526, 21H1 10.0.19043.1526, 21H2 10.0.19044.1526, Windows 11 21H2 10.0.22000.493. Look up the exact KB per edition in the Microsoft Security Update Guide.
- Verify build compliance across the estate, e.g. in Defender for Endpoint:
DeviceInfo | where OSPlatform startswith "Windows" | summarize arg_max(Timestamp, OSBuild, OSVersionInfo) by DeviceName. Remediate the most exposed systems first: mail- and Office-heavy workstations, then RDS/Citrix hosts on Server 2019. - Identify hosts still running Windows 10 1909, 20H2 or 21H1. These versions are out of support. Schedule them for upgrade and isolate them in the meantime.
- Exploitation requires user interaction via a crafted file; public PoC analysis uses an Office/RTF document. Temporarily quarantine or sanitise (CDR) inbound RTF, legacy DOC and DOCX attachments with embedded OLE objects from external senders at the mail gateway.
- Send a short advisory to users and the service desk: do not open unexpected document attachments, and report Word or Outlook crashes that happen when opening a file.
Runbook step 2
Mitigation layers
- Endpoint hardening (ASR): Enable the Defender ASR rules "Block all Office applications from creating child processes" (
d4f940ab-401b-4efc-aadc-ad5f3c50688d) and "Block Office applications from injecting code into other processes" (75668c1f-73b5-4cf5-bb93-3ecf5cb7cc84) in block mode, or at least audit mode. - Office configuration: Use GPO or Intune File Block Settings so RTF and legacy formats open only in Protected View, or not at all. Enforce Protected View for internet-origin files and Outlook attachments, and make sure archive tools propagate Mark-of-the-Web.
- Application control: Deploy WDAC or AppLocker rules that block execution from user-writable paths (
%APPDATA%,%TEMP%,Downloads). This breaks the second-stage payload. - Least privilege: Remove local admin rights and manage the remaining local accounts with Windows LAPS. Code runs as the logged-on user, so non-admin users sharply limit the blast radius.
- Network segmentation: Move unpatched legacy hosts into a dedicated VLAN with no direct internet egress (authenticated proxy only) and no SMB/RDP access into server segments.
- Endpoint hardening (ASR): Enable the Defender ASR rules "Block all Office applications from creating child processes" (
Runbook step 3
Detection rules
- Sysmon EID 1 / EDR process ancestry:
WINWORD.EXE,EXCEL.EXEorOUTLOOK.EXEspawningcmd.exe,powershell.exe,rundll32.exe,regsvr32.exe,mshta.exeorwscript.exe. Sigma shape:ParentImage|endswith: '\WINWORD.EXE' and Image|endswith: ['\cmd.exe','\powershell.exe','\rundll32.exe']. - Sysmon EID 7 (image load): An Office process loading
prauthproviders.dll, which is unusual for Word and matches the public PoC analysis. KQL:DeviceImageLoadEvents | where InitiatingProcessFileName =~ "winword.exe" and FileName =~ "prauthproviders.dll". - Application log Event ID 1000/1001:
WINWORD.EXEcrashing with faulting moduleprauthproviders.dllorcombase.dll, which may indicate failed exploitation attempts. Correlate hits with the attachment delivered just before the crash. - Defender ASR events (Microsoft-Windows-Windows Defender/Operational, EID 1121/1122): Blocked or audited Office child processes. Treat as high priority when they occur shortly after mail delivery.
- Network (Zeek/proxy): Outbound HTTP(S) from Office processes or their children to newly registered or rarely seen domains within minutes of a document being opened.
- Sysmon EID 1 / EDR process ancestry:
Detection rules
No NEOSEC detection rule is available for this vulnerability yet.
Classification under NIS2 and CRA
Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.
NIS2
NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.
Read in glossary- Actively exploited: treat the vulnerability as a priority in vulnerability handling under Art. 21(2)(e) NIS2. If it is exploited in your environment, check the reporting obligation under Art. 23 (early warning within 24 hours).
CRA
The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.
Read in glossary- Since 11.09.2026, manufacturers of affected products with digital elements must report actively exploited vulnerabilities under Art. 14 CRA, with an early warning within 24 hours via ENISA's single reporting platform.
ISO/IEC 27001
ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.
Read in glossary- Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.
Description
Windows Runtime Remote Code Execution Vulnerability
Source: CSA/SingCERT, NVD (NIST), cvelistv5, CISA KEV Catalog, CVE.org (MITRE)
Affected products
The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.
| Affected versions | Fixed in | ||
|---|---|---|---|
| Microsoft | Windows 10 Version 1809 |
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|
| Microsoft | Windows 10 Version 1909 |
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| Microsoft | Windows 10 Version 20H2 |
|
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| Microsoft | Windows 10 Version 21H1 |
|
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| Microsoft | Windows 10 Version 21H2 |
|
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| Microsoft | Windows 11 version 21H2 |
|
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| Microsoft | Windows Server 2019 |
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| Microsoft | Windows Server 2019 (Server Core installation) |
|
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| Microsoft | Windows Server 2022 |
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| Microsoft | Windows Server version 20H2 |
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|
Vendors and products
- Microsoft Microsoft Windows 10 1809
- Microsoft Windows 10 1909
- Microsoft Windows 10 20h2
- Microsoft Windows 10 21h1
- Microsoft Microsoft Windows 10 21H2
- Microsoft Windows 10 Version 1809
- Microsoft Windows 10 Version 1909
- Microsoft Windows 10 Version 20h2
- Microsoft Windows 10 Version 21h1
- Microsoft Windows 10 Version 21h2
- Microsoft Windows 11 21h2
- Microsoft Windows 11 Version 21h2
Affected operating systems
| Windows | microsoft | windows_10_1809 | — |
| Windows | microsoft | windows_10_1909 | — |
| Windows | microsoft | windows_10_20h2 | — |
| Windows | microsoft | windows_10_21h1 | — |
| Windows | microsoft | windows_10_21h2 | — |
| Windows | microsoft | windows_11_21h2 | — |
| Windows | microsoft | windows_server_2019 | — |
| Windows | microsoft | windows_server_2022 | — |
| Windows | microsoft | windows_server_20h2 | — |
Public exploit references
Publicly reported proof-of-concepts, exploit modules and detection templates for this vulnerability. NEOSEC links to the original sources only and does not provide any exploit code.
| CISA KEV Catalog | CISA Known Exploited Vulnerability (opens in a new tab)cisa.gov | actively exploited | |
| CSA/SingCERT | Active Exploitation of Vulnerabilities in Apple, Google, Microsoft, Palo Alto and SAP products (opens in a new tab)CSA/SingCERT | actively exploited |
References & sources
- Microsoft Security Update GuideWindows Runtime Remote Code Execution VulnerabilityVendor advisory, Patch, Vendor advisory
- cisa.govknown-exploited-vulnerabilities-catalog?field_cve=CVE-2022-21971government-resource, US government resource
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<a href="https://intel.neosec.eu/en/cve/CVE-2022-21971"><img src="https://intel.neosec.eu/badge/cve/CVE-2022-21971.svg?lang=en" alt="CVE-2022-21971 – NEOSEC Intel" height="20"></a>