CVE-2023-28219: Windows 10 1507 L2TP RCE Vulnerability

CVE-2023-28219 Overview

CVE-2023-28219 is a Remote Code Execution (RCE) vulnerability affecting the Layer 2 Tunneling Protocol (L2TP) implementation in Microsoft Windows operating systems. This vulnerability allows an unauthenticated attacker to execute arbitrary code on vulnerable systems by sending specially crafted L2TP traffic over the network. L2TP is widely deployed in enterprise environments for VPN connectivity, making this vulnerability particularly concerning for organizations relying on Windows-based VPN infrastructure.

Critical Impact

Successful exploitation enables remote code execution without authentication, potentially allowing attackers to gain complete control over affected Windows systems through network-based attacks targeting L2TP services.

Affected Products

• Microsoft Windows 10 (versions 1507, 1607, 1809, 20H2, 21H2, 22H2)
• Microsoft Windows 11 (versions 21H2, 22H2)
• Microsoft Windows Server 2008 (SP2 and R2 SP1)
• Microsoft Windows Server 2012 (including R2)
• Microsoft Windows Server 2016
• Microsoft Windows Server 2019
• Microsoft Windows Server 2022

Discovery Timeline

• April 11, 2023 - CVE-2023-28219 published to NVD
• November 21, 2024 - Last updated in NVD database

Technical Details for CVE-2023-28219

Vulnerability Analysis

This vulnerability resides in the Windows Layer 2 Tunneling Protocol implementation and is classified under CWE-591 (Sensitive Data Storage in Improperly Locked Memory). The flaw allows remote attackers to execute arbitrary code on target systems without requiring any prior authentication or user interaction. However, exploitation requires winning a race condition, which adds complexity to successful attacks.

The vulnerability affects the kernel-level handling of L2TP protocol packets. When processing specially crafted L2TP traffic, the affected Windows component fails to properly manage memory operations, creating conditions that can be exploited to achieve code execution in the context of the system. The network-based attack vector means that any system with L2TP services exposed to untrusted networks is potentially at risk.

Root Cause

The root cause of CVE-2023-28219 lies in improper memory handling within the L2TP protocol implementation. Specifically, the vulnerability stems from sensitive data being stored in improperly locked memory (CWE-591), which can lead to race conditions during memory access. When processing L2TP protocol messages, the system fails to properly synchronize memory operations, allowing an attacker to manipulate memory contents and redirect execution flow.

Attack Vector

The vulnerability is exploitable over the network without requiring authentication or user interaction. An attacker would need to send specially crafted L2TP packets to a vulnerable Windows system. The attack complexity is high due to the requirement to win a race condition during exploitation. Successful exploitation results in complete compromise of the affected system with high impact to confidentiality, integrity, and availability.

The attack scenario involves:

1. Identifying a Windows system with L2TP services accessible over the network
2. Crafting malicious L2TP protocol packets designed to trigger the memory handling flaw
3. Sending the packets while timing the attack to win the race condition
4. Achieving arbitrary code execution in the system context upon successful exploitation

Detection Methods for CVE-2023-28219

Indicators of Compromise

• Unexpected L2TP traffic patterns or malformed L2TP packets targeting port 1701/UDP
• System crashes or kernel errors related to L2TP protocol handling (raspptp.sys or rasl2tp.sys)
• Unusual process creation or network activity following L2TP service interactions
• Windows Event Log entries indicating memory access violations in network protocol handlers

Detection Strategies

• Deploy network intrusion detection systems (IDS) with signatures for anomalous L2TP protocol traffic
• Enable Windows Defender Exploit Guard with Attack Surface Reduction rules for network protocol handlers
• Monitor for crash dumps and kernel mode exceptions related to L2TP driver components
• Implement SentinelOne's behavioral AI to detect post-exploitation activities and memory manipulation attempts

Monitoring Recommendations

• Enable detailed logging for Remote Access Services and VPN components in Windows Event Logs
• Configure network monitoring to alert on high volumes of L2TP traffic from unusual sources
• Implement SentinelOne Singularity platform for real-time kernel-level threat detection
• Monitor system stability metrics for L2TP-related service crashes that may indicate exploitation attempts

How to Mitigate CVE-2023-28219

Immediate Actions Required

• Apply Microsoft's security update for CVE-2023-28219 immediately on all affected Windows systems
• Restrict network access to L2TP services (UDP port 1701) using firewall rules to trusted networks only
• Consider disabling L2TP VPN services on systems where not required until patches can be applied
• Enable SentinelOne's Singularity XDR for comprehensive endpoint protection against exploitation attempts

Patch Information

Microsoft has released security updates addressing this vulnerability as part of their April 2023 security updates. System administrators should consult the Microsoft Security Advisory for detailed patch information and download links specific to their Windows versions. The patches address the underlying memory handling issues in the L2TP protocol implementation.

Updates are available through:

• Windows Update
• Microsoft Update Catalog
• Windows Server Update Services (WSUS)
• Microsoft Endpoint Configuration Manager

Workarounds

• Disable the L2TP VPN service if not actively required: Set-Service -Name "RasMan" -StartupType Disabled
• Block UDP port 1701 at perimeter firewalls to prevent external exploitation attempts
• Implement network segmentation to limit L2TP service exposure to trusted internal networks only
• Use alternative VPN solutions such as IKEv2 or SSTP while awaiting patch deployment

# Disable L2TP/IPsec VPN service via PowerShell
Stop-Service -Name "RasMan" -Force
Set-Service -Name "RasMan" -StartupType Disabled

# Block L2TP port at Windows Firewall
New-NetFirewallRule -DisplayName "Block L2TP Inbound" -Direction Inbound -Protocol UDP -LocalPort 1701 -Action Block