CVE-2022-21971: Windows 10 1809 RCE Vulnerability

CVE-2022-21971 Overview

CVE-2022-21971 is a Windows Runtime remote code execution vulnerability affecting multiple Windows 10, Windows 11, and Windows Server versions. The flaw is tracked under [CWE-824] (Access of Uninitialized Pointer) and requires local access combined with user interaction to trigger. An attacker who convinces a user to open a crafted file or content can execute arbitrary code in the context of the current user. CISA added this vulnerability to its Known Exploited Vulnerabilities catalog, confirming active in-the-wild exploitation.

Critical Impact
Successful exploitation allows arbitrary code execution on affected Windows systems, leading to full compromise of confidentiality, integrity, and availability under the user's privileges.

Affected Products

Microsoft Windows 10 (versions 1809, 1909, 20H2, 21H1, 21H2)
Microsoft Windows 11 21H2
Microsoft Windows Server 2019, Server 2022, and Server 20H2

Discovery Timeline

2022-02-09 - CVE-2022-21971 published to the National Vulnerability Database
2022-02-09 - Microsoft released a security update via the Microsoft Security Response Center advisory
2025-10-30 - Last updated in NVD database

Technical Details for CVE-2022-21971

Vulnerability Analysis

The vulnerability resides in the Windows Runtime (WinRT) component, which provides the application programming interface used by modern Windows applications. The flaw is classified as [CWE-824], indicating that the runtime accesses a pointer before it has been properly initialized. When this uninitialized pointer is dereferenced during the processing of attacker-supplied content, control flow can be redirected to attacker-controlled memory.

Exploitation produces remote code execution at the privilege level of the logged-on user. While the attack vector is local and requires the user to open a crafted file or invoke specific application functionality, the EPSS probability of 87.787% (99th percentile) reflects the high likelihood of exploit activity. CISA's inclusion of this CVE in the Known Exploited Vulnerabilities catalog confirms that threat actors have weaponized the flaw.

Root Cause

The root cause is improper initialization of a pointer within the Windows Runtime subsystem. When the runtime parses certain object structures, an internal pointer field is consumed before it has been assigned a valid address. Dereferencing that uninitialized value during method dispatch or object resolution allows attacker-influenced data to be treated as a valid object reference.

Attack Vector

The attack vector is local with required user interaction. An attacker delivers a crafted file or content using phishing, removable media, or a malicious download. When the victim opens the content with an application that invokes the vulnerable Windows Runtime code path, the uninitialized pointer is dereferenced and the attacker gains code execution. No pre-existing privileges are required on the target host. Public technical exploitation details remain limited; refer to the Microsoft Security Update and the CISA Known Exploited Vulnerability listing for vendor-confirmed details.

Detection Methods for CVE-2022-21971

Indicators of Compromise

Unexpected child processes spawned by applications that consume Windows Runtime APIs, such as explorer.exe, Office processes, or UWP application hosts
Crashes or anomalous module loads referencing Windows Runtime libraries (for example combase.dll or Windows.UI.*) shortly before suspicious process creation
Outbound network connections from user-mode applications immediately after opening attachments or downloaded content
New persistence entries (Run keys, scheduled tasks) created by processes that should not normally write to these locations

Detection Strategies

Monitor process lineage for Windows Runtime host processes spawning shells (cmd.exe, powershell.exe) or LOLBins (rundll32.exe, regsvr32.exe)
Hunt for crash telemetry in Windows Error Reporting tied to WinRT modules paired with subsequent code execution
Correlate file-open events with anomalous in-memory module loads in user-mode application contexts

Monitoring Recommendations

Ingest Sysmon Event IDs 1 (process creation), 7 (image load), and 11 (file create) into your SIEM for behavioral correlation
Track Windows Defender and EDR alerts referencing Windows Runtime components or UWP application hosts
Audit endpoints to confirm February 2022 cumulative updates are installed, and alert when patch levels regress

How to Mitigate CVE-2022-21971

Immediate Actions Required

Apply the February 2022 Microsoft security updates referenced in the MSRC advisory to all affected Windows 10, Windows 11, and Windows Server systems
Prioritize remediation for internet-facing user workstations and systems where users open files from external sources
Validate patch deployment against the CISA KEV catalog due-date guidance for federal and regulated environments

Patch Information

Microsoft addressed CVE-2022-21971 in the February 2022 Patch Tuesday cumulative updates. Administrators should consult the Microsoft Security Update Guide for the specific KB articles applicable to each affected build. Cumulative updates released after February 2022 also include the fix.

Workarounds

No official vendor workaround is published; patching is the only supported remediation
Restrict the opening of untrusted files and attachments through email security gateways and attachment sandboxing
Enforce least-privilege user accounts so that successful exploitation does not yield administrative privileges
Deploy application allowlisting (Windows Defender Application Control or AppLocker) to limit execution of unsigned binaries

bash

# Verify the patch is installed (PowerShell)
Get-HotFix | Where-Object { $_.InstalledOn -ge (Get-Date '2022-02-08') } | Sort-Object InstalledOn