CVE-2022-21922: Microsoft Windows 10 RCE Vulnerability

CVE-2022-21922 Overview

CVE-2022-21922 is a Remote Code Execution vulnerability affecting the Remote Procedure Call (RPC) Runtime component in Microsoft Windows operating systems. This vulnerability allows an authenticated attacker to execute arbitrary code on affected systems over the network by sending specially crafted RPC requests to vulnerable endpoints.

The RPC Runtime is a fundamental Windows component that enables inter-process communication across networked systems. Exploitation of this vulnerability could allow an attacker to execute code with the privileges of the RPC service, potentially leading to full system compromise.

Critical Impact

Authenticated attackers can achieve remote code execution across the network, compromising confidentiality, integrity, and availability of affected Windows systems.

Affected Products

• Microsoft Windows 10 (multiple versions including 1607, 1809, 1909, 20H2, 21H1, 21H2)
• Microsoft Windows 11 (x64 and ARM64)
• Microsoft Windows 7 SP1
• Microsoft Windows 8.1
• Microsoft Windows Server 2008 SP2 and R2 SP1
• Microsoft Windows Server 2012 and R2
• Microsoft Windows Server 2016
• Microsoft Windows Server 2019
• Microsoft Windows Server 2022 and 20H2

Discovery Timeline

• 2022-01-11 - CVE-2022-21922 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2022-21922

Vulnerability Analysis

This Remote Code Execution vulnerability resides in the Windows RPC Runtime, a core operating system service responsible for facilitating communication between processes across network boundaries. The vulnerability can be exploited by an authenticated user over the network without requiring user interaction.

The attack requires low privileges to execute, meaning any authenticated domain user or local user with network access could potentially exploit this vulnerability. Successful exploitation grants the attacker the ability to execute arbitrary code on the target system, potentially with elevated privileges depending on the context of the RPC service being targeted.

The vulnerability affects a wide range of Windows operating systems, from legacy Windows 7 SP1 systems to the latest Windows 11 and Windows Server 2022 releases, indicating that the vulnerable code has been present in the RPC Runtime for an extended period.

Root Cause

The vulnerability stems from improper handling of RPC requests within the Windows RPC Runtime. While Microsoft has not disclosed specific technical details about the root cause (classified as NVD-CWE-noinfo), the nature of the vulnerability as a remote code execution flaw in RPC typically involves issues such as:

• Improper validation of RPC request parameters
• Memory corruption during RPC message processing
• Insufficient bounds checking on serialized data structures

The RPC Runtime processes incoming network requests and deserializes data that may contain malicious payloads crafted to corrupt memory or redirect code execution.

Attack Vector

The attack is network-based and requires:

1. Network Access: The attacker must be able to reach the target system over the network on RPC-related ports (typically TCP port 135 for RPC endpoint mapper, plus dynamically assigned ports)
2. Authentication: Low-level authentication is required, which could be any valid domain or local user credentials
3. No User Interaction: Exploitation does not require any action from the victim user

An attacker would craft malicious RPC requests targeting vulnerable endpoints on the Windows RPC Runtime. Upon processing these requests, the vulnerable code could be triggered, leading to arbitrary code execution on the target system.

For technical details and exploitation specifics, refer to the Microsoft Security Advisory.

Detection Methods for CVE-2022-21922

Indicators of Compromise

• Anomalous RPC traffic patterns on TCP port 135 and high dynamic port ranges (49152-65535)
• Unexpected process creation events spawned from RPC-related services such as svchost.exe hosting RPC components
• Suspicious memory access patterns or crashes in rpcrt4.dll or related RPC runtime components
• Authentication events from unexpected sources attempting to access RPC endpoints

Detection Strategies

• Monitor network traffic for unusual RPC-related communications, particularly high volumes of requests to TCP port 135 and dynamic RPC ports
• Implement endpoint detection rules to identify anomalous behavior from RPC runtime processes
• Deploy SIEM rules to correlate authentication events with subsequent suspicious process execution
• Use Windows Event Logs to track RPC service errors and security audit events (Event IDs 5145, 5156, 5158)

Monitoring Recommendations

• Enable advanced auditing for object access and process creation on Windows systems
• Configure network intrusion detection systems to alert on malformed RPC packets
• Implement behavioral analysis to detect code execution chains originating from RPC services
• Regularly review security logs for authentication attempts from unusual network segments

How to Mitigate CVE-2022-21922

Immediate Actions Required

• Apply the January 2022 Microsoft security updates to all affected Windows systems immediately
• Prioritize patching internet-facing systems and servers with RPC endpoints exposed
• Restrict RPC traffic at network perimeters using firewall rules to limit exposure
• Review and limit user accounts with network access privileges to reduce the attack surface

Patch Information

Microsoft has released security updates addressing this vulnerability as part of the January 2022 Patch Tuesday release cycle. Patches are available through Windows Update, Microsoft Update Catalog, and Windows Server Update Services (WSUS) for all affected operating system versions.

For detailed patch information and download links, consult the Microsoft Update Guide for CVE-2022-21922.

Workarounds

• Implement network segmentation to restrict RPC traffic between network zones and limit lateral movement opportunities
• Use Windows Firewall to block inbound RPC traffic on non-essential systems where RPC services are not required
• Disable unnecessary RPC endpoints and services to reduce the attack surface on critical systems
• Consider implementing IPsec or other network-layer encryption to protect RPC communications

# Block inbound RPC traffic on Windows Firewall (PowerShell)
# Only apply this on systems where RPC is not required
New-NetFirewallRule -DisplayName "Block RPC Endpoint Mapper" -Direction Inbound -LocalPort 135 -Protocol TCP -Action Block