CVE-2024-40765: SonicOS IPSec RCE Vulnerability

CVE-2024-40765 Overview

An Integer-based buffer overflow vulnerability exists in SonicOS via IPSec that allows a remote attacker, under specific conditions, to cause Denial of Service (DoS) and potentially execute arbitrary code by sending a specially crafted IKEv2 payload. This vulnerability affects the network perimeter security of organizations relying on SonicWall firewall appliances for IPSec VPN connectivity.

Critical Impact

Remote unauthenticated attackers can potentially achieve code execution on affected SonicWall devices by exploiting the integer overflow in IKEv2 payload processing, compromising network gateway security.

Affected Products

• SonicWall SonicOS (specific affected versions detailed in vendor advisory)
• SonicWall firewall appliances with IPSec VPN enabled
• Devices processing IKEv2 protocol connections

Discovery Timeline

• 2025-01-09 - CVE CVE-2024-40765 published to NVD
• 2025-01-09 - Last updated in NVD database

Technical Details for CVE-2024-40765

Vulnerability Analysis

This vulnerability stems from an integer-based buffer overflow (CWE-190) in the SonicOS IPSec implementation. When processing IKEv2 (Internet Key Exchange version 2) payloads, the affected code fails to properly validate integer values used in buffer size calculations. An attacker can craft malicious IKEv2 packets that trigger an integer overflow condition, causing the system to allocate an incorrectly sized buffer. Subsequent operations then write beyond the allocated memory boundaries.

The vulnerability is exploitable remotely over the network without requiring authentication or user interaction. This makes it particularly dangerous for internet-facing SonicWall appliances that have IPSec VPN services enabled. Successful exploitation could allow an attacker to crash the device (DoS) or potentially achieve arbitrary code execution with the privileges of the SonicOS process.

Root Cause

The root cause is an integer overflow vulnerability (CWE-190) in the IKEv2 payload parsing logic within SonicOS. When calculating buffer sizes based on attacker-controlled length fields in IKEv2 packets, the code performs arithmetic operations that can overflow integer boundaries. This results in a smaller-than-expected buffer allocation, leading to a buffer overflow when the actual payload data is copied.

Attack Vector

The attack vector is network-based, targeting the UDP port 500 (IKE) or UDP port 4500 (IKE NAT-T) services on vulnerable SonicWall devices. An unauthenticated remote attacker sends specially crafted IKEv2 packets containing malformed payload length values designed to trigger the integer overflow condition. The attack requires no prior authentication and no user interaction, making it highly accessible to attackers who can reach the target device over the network.

The exploitation mechanism involves:

1. Identifying a SonicWall device with IPSec VPN services exposed
2. Constructing IKEv2 packets with payload length fields designed to cause integer overflow
3. Sending the malicious packets to the target device's IKE service
4. Triggering buffer corruption that leads to DoS or code execution

Detection Methods for CVE-2024-40765

Indicators of Compromise

• Unexpected SonicWall device crashes or reboots, particularly when processing VPN connections
• Anomalous IKEv2 traffic patterns with unusually large or malformed payload length values
• System logs indicating memory corruption or segmentation faults in IPSec-related processes
• Unexpected network traffic originating from the SonicWall management interface

Detection Strategies

• Monitor IKEv2 traffic (UDP 500/4500) for packets with anomalous payload sizes or malformed structures
• Implement network intrusion detection rules to identify potential integer overflow exploitation attempts in IKE traffic
• Configure alerts for unexpected SonicWall device restarts or service interruptions
• Deploy SentinelOne Singularity to detect post-exploitation activities and lateral movement attempts

Monitoring Recommendations

• Enable comprehensive logging on SonicWall devices for VPN and IPSec events
• Implement network-level monitoring for IKEv2 protocol anomalies using tools like Zeek or Suricata
• Configure SIEM rules to correlate multiple device crashes with incoming IKEv2 traffic patterns
• Monitor for reconnaissance activity targeting UDP ports 500 and 4500

How to Mitigate CVE-2024-40765

Immediate Actions Required

• Review the SonicWall Vulnerability Advisory SNWLID-2024-0013 for specific patch information
• Identify all SonicWall devices with IPSec VPN services enabled in your environment
• Prioritize patching internet-facing devices immediately
• Consider temporarily disabling IPSec VPN services on critical devices until patches can be applied

Patch Information

SonicWall has released a security advisory addressing this vulnerability. Administrators should consult the SonicWall PSIRT Advisory SNWLID-2024-0013 for specific firmware versions that contain the fix. Apply the latest SonicOS firmware version recommended by SonicWall for your device model.

Workarounds

• Restrict access to IKEv2 services (UDP 500/4500) to known, trusted IP addresses using access control lists
• If IPSec VPN is not required, disable the service entirely on affected devices
• Implement additional network segmentation to limit exposure of vulnerable devices
• Deploy upstream IPS/IDS rules to filter potentially malicious IKEv2 traffic before it reaches SonicWall devices

# Example: Restrict IKE access to specific source IPs (verify syntax with SonicWall documentation)
# This is a conceptual example - consult SonicWall documentation for actual CLI syntax
# Limit IPSec VPN access to trusted remote networks only
# Implement geo-blocking for IKE services where appropriate