CVE-2023-28250: Windows PGM RCE Vulnerability

CVE-2023-28250 Overview

CVE-2023-28250 is a critical remote code execution vulnerability affecting the Windows Pragmatic General Multicast (PGM) protocol implementation. PGM is a reliable multicast transport protocol that enables receivers to detect loss, request retransmission of lost data, or notify an application of unrecoverable loss. This vulnerability allows unauthenticated attackers to execute arbitrary code on affected Windows systems over the network without requiring any user interaction.

The vulnerability exists in the Windows implementation of PGM, which is enabled when the Message Queuing (MSMQ) service is running. When PGM is active, an attacker can send specially crafted network packets to trigger the vulnerability and gain complete control over the target system with SYSTEM-level privileges.

Critical Impact

This vulnerability enables unauthenticated remote code execution with no user interaction required. Attackers can gain complete system control over Windows systems where Message Queuing services are enabled.

Affected Products

• Microsoft Windows 10 (versions 1507, 1607, 1809, 20H2, 21H2, 22H2)
• Microsoft Windows 11 (versions 21H2, 22H2)
• Microsoft Windows Server 2008, 2008 R2, 2012, 2012 R2, 2016, 2019, 2022

Discovery Timeline

• April 11, 2023 - CVE-2023-28250 published to NVD
• November 21, 2024 - Last updated in NVD database

Technical Details for CVE-2023-28250

Vulnerability Analysis

This vulnerability is classified as CWE-191 (Integer Underflow), a memory corruption issue that occurs when an arithmetic operation produces a value smaller than the minimum allowed for the destination integer type. In the context of the Windows PGM implementation, this integer underflow condition can be exploited to corrupt memory and hijack program execution flow.

The attack is network-based and requires no authentication or user interaction, making it particularly dangerous for systems exposed to untrusted networks. The vulnerability affects the core Windows operating system component responsible for handling PGM multicast traffic, specifically when the Message Queuing (MSMQ) Windows component is enabled.

Successful exploitation grants attackers complete control over the compromised system, including the ability to read and modify sensitive data, install malware, create new accounts with elevated privileges, and pivot to other systems on the network.

Root Cause

The root cause is an integer underflow vulnerability (CWE-191) in the Windows PGM protocol handler. When processing certain PGM packets, the code performs arithmetic operations on size or length values without proper boundary validation. This allows an attacker to craft malicious packets that cause an integer underflow, leading to incorrect memory allocation sizes or buffer boundary calculations.

The integer underflow can result in:

• Allocation of undersized buffers
• Buffer overflows during subsequent data copy operations
• Heap corruption enabling arbitrary code execution

Attack Vector

The attack vector is network-based, targeting systems with the Windows Message Queuing (MSMQ) service enabled. The attacker sends specially crafted PGM multicast packets to the vulnerable system over the network.

The attack requires:

1. Target system has MSMQ service installed and running
2. PGM protocol support is enabled (typically port 3389 or custom MSMQ ports)
3. Network connectivity to the target system
4. No authentication or user interaction required

An attacker positioned on the same network segment, or with routing access to the target, can exploit this vulnerability by sending malicious PGM packets that trigger the integer underflow condition, ultimately achieving remote code execution with SYSTEM privileges.

Detection Methods for CVE-2023-28250

Indicators of Compromise

• Unusual network traffic on MSMQ ports (typically TCP 1801, UDP 3527, or custom configured ports)
• Unexpected PGM multicast traffic from external or suspicious IP addresses
• Crashes or unexpected restarts of the mqsvc.exe (Message Queuing) service
• Evidence of code execution originating from MSMQ service processes
• Anomalous child processes spawned from mqsvc.exe

Detection Strategies

• Monitor for abnormal PGM/multicast traffic patterns using network intrusion detection systems
• Implement endpoint detection rules for suspicious process behavior related to mqsvc.exe
• Deploy memory protection controls that can detect heap corruption and exploitation attempts
• Use SentinelOne's behavioral AI to identify exploitation attempts targeting the MSMQ service
• Configure alerts for unexpected service crashes or restarts of Message Queuing services

Monitoring Recommendations

• Enable detailed logging for MSMQ service activities and network connections
• Implement network segmentation to limit exposure of MSMQ services to trusted networks only
• Monitor for reconnaissance activity targeting MSMQ ports and PGM protocol endpoints
• Regularly audit systems for unnecessary MSMQ service installations

How to Mitigate CVE-2023-28250

Immediate Actions Required

• Apply the Microsoft security update immediately on all affected Windows systems
• Disable the Message Queuing (MSMQ) service on systems where it is not required
• Block PGM and MSMQ traffic at network perimeters if the service is not business-critical
• Implement network segmentation to isolate systems running MSMQ from untrusted networks
• Deploy SentinelOne endpoint protection for real-time detection and prevention of exploitation attempts

Patch Information

Microsoft has released security updates to address CVE-2023-28250 as part of their April 2023 Patch Tuesday release. Organizations should obtain the appropriate patches from the Microsoft Security Update Guide for their specific Windows versions and apply them immediately.

The patch addresses the integer underflow vulnerability in the PGM protocol handler, implementing proper boundary validation for arithmetic operations that previously allowed the vulnerability to be triggered.

Workarounds

• Disable the Message Queuing Windows feature if not required for business operations
• Use Windows Firewall to block inbound PGM and MSMQ traffic from untrusted networks
• Implement network access controls to restrict access to MSMQ services to authorized systems only
• Consider using IPsec or other network-level authentication for MSMQ communications

# Check if MSMQ is installed
Get-WindowsFeature -Name MSMQ*

# Disable MSMQ service if not required
Stop-Service -Name MSMQ -Force
Set-Service -Name MSMQ -StartupType Disabled

# Block MSMQ ports via Windows Firewall (example)
New-NetFirewallRule -DisplayName "Block MSMQ Inbound" -Direction Inbound -LocalPort 1801,3527 -Protocol TCP -Action Block
New-NetFirewallRule -DisplayName "Block MSMQ UDP Inbound" -Direction Inbound -LocalPort 3527 -Protocol UDP -Action Block