In January 2022, Microsoft patched a dangerous vulnerability—CVE-2022-21874—that could allow remote code execution through the Windows Security Center API. This flaw flew under the radar for a while, but if you’re managing Windows endpoints or writing system-level tools, you should understand what went wrong, how attackers might abuse it, and how to defend yourself.

In this long read, you’ll get an exclusive, plain-English walkthrough of how CVE-2022-21874 works, sample code of the vulnerable API interaction, and pointers to further research—including sources from Microsoft and the infosec community.

What is CVE-2022-21874?

CVE-2022-21874 is a vulnerability in the Windows Security Center (WSC) API, a core part of Windows that tracks system health features like antivirus, firewall, and updates. The core problem: If an attacker tricks a privileged process into making certain WSC API calls, they can execute code with SYSTEM-level privileges.

Severity: | Score:  
:--- | :---  
Remote Code Execution (RCE) | 7.8 (High)  
Patch Release Date: | January 11, 2022  

Microsoft Security Bulletin:  
Microsoft Security Advisory: CVE-2022-21874

The WSC API: A Quick Overview

The Security Center API lets third-party antivirus and firewall products tell Windows about their status, update notifications, and more. At the heart of this system is the wscsvc (Windows Security Center Service), which exposes named pipes and APIs for communication.

An attacker, under certain circumstances, could exploit a race condition or improper impersonation in this API communication, leading a privileged Windows process (like AV or management tools running as SYSTEM) to execute malicious code controlled by a low-privilege attacker.

Core Problem: Improper Impersonation

Impersonation in Windows means running a set of actions as if you were another user. Secure APIs must check “who’s really making this call?” and drop privileges if needed. If done wrong, malicious actors can trick a SYSTEM-privileged service into running malicious code on their behalf.

Attack Scenarios

1. Local Elevation of Privileges (EoP):  
If a non-admin user can get a privileged process to connect to a crafted named pipe, and the WSC API does not correctly impersonate the original user, SYSTEM-level code execution can be triggered.

2. Remote Code Execution (RCE):  
In certain remote scenarios (LAN, domain environments), an attacker who can interact with WSC endpoints might get code executed at SYSTEM, depending on process trust and configuration.

Example: Simulating the Vulnerability (Simplified)

The true exploit code is dangerous, so here's a sanitized snippet in C-like pseudocode to illustrate the flaw.

Suppose a WSC API call looks like this

// On a privileged service
HANDLE pipe = CreateNamedPipe("\\\\.\\pipe\\wsc_pipe", ...);

// Attacker connects...
ConnectNamedPipe(pipe, NULL);

// Vulnerable impersonation sequence
ImpersonateNamedPipeClient(pipe);

// (Missing: CheckTokenInformation here)

// Now, read a command provided by the attacker
CHAR buffer[256];
ReadFile(pipe, buffer, sizeof(buffer), NULL, NULL);

// Use the data in a privileged context - DANGER!
system(buffer);  // This could now run as SYSTEM!

Where’s the problem?
The service uses ImpersonateNamedPipeClient, but doesn’t check the caller’s identity before executing attacker-controlled data under SYSTEM privileges.

Real-World Exploit Steps

While a full public PoC has not been responsibly released, researchers have confirmed practical abuse. Here’s the general method (don’t abuse this!):

Mitigation

The Fix:  
Microsoft patched the API to strictly verify client tokens and enforce correct impersonation. Always apply Windows updates regularly!

- Bulletin: MSRC CVE-2022-21874

Microsoft Official:

- CVE-2022-21874
 - Microsoft Patch Tuesday - January 2022

Security Research:

- Hacker News Writeup
 - WSC API Documentation

Conclusion

CVE-2022-21874 is a great reminder: even trusted Windows system APIs can be sources of privilege escalation and remote code execution if not implemented carefully. As always, keep your systems updated, review privileged service code for impersonation mishaps, and treat inter-process APIs with great care.


*Stay safe and patched, and keep learning about the security foundations under every Windows button you click.*

Timeline

Published on: 01/11/2022 21:15:00 UTC
Last modified on: 05/23/2022 17:29:00 UTC