CVE-2024-40765: SonicOS IPSec RCE Vulnerability

CVE-2024-40765 Overview

CVE-2024-40765 is an integer-based buffer overflow vulnerability in SonicWall SonicOS affecting the IPSec implementation. A remote unauthenticated attacker can trigger the flaw by sending a specially crafted Internet Key Exchange version 2 (IKEv2) payload. Successful exploitation causes Denial of Service (DoS) and may allow arbitrary code execution under specific conditions. The vulnerability is classified under [CWE-190] (Integer Overflow or Wraparound) and impacts SonicOS firewall appliances exposing IKEv2 services. SonicWall published advisory SNWLID-2024-0013 to address the issue. Given that affected devices are typically internet-facing perimeter firewalls, exposure to opportunistic scanning and exploitation attempts is high.

Critical Impact

Remote unauthenticated attackers can crash SonicOS firewalls or potentially execute arbitrary code, compromising perimeter defenses and enabling lateral movement into internal networks.

Affected Products

• SonicWall SonicOS (IPSec/IKEv2 component)
• SonicWall firewall appliances with IPSec VPN enabled
• Refer to SNWLID-2024-0013 for the complete list of affected firmware versions

Discovery Timeline

• 2025-01-09 - CVE-2024-40765 published to NVD
• 2026-04-15 - Last updated in NVD database

Technical Details for CVE-2024-40765

Vulnerability Analysis

The vulnerability resides in the IKEv2 payload parsing logic within the SonicOS IPSec subsystem. IKEv2 is the protocol used to negotiate Security Associations for IPSec VPN tunnels. SonicOS processes attacker-supplied IKEv2 payloads during the negotiation phase before authentication completes, which makes the code path reachable by any remote host that can deliver UDP packets to the IKE listener.

An integer overflow during size calculation produces an undersized buffer allocation. Subsequent copy operations then write beyond the allocated region, corrupting adjacent heap memory. The immediate consequence is a process crash that takes the firewall offline. Depending on heap layout and memory protections, the corruption may also be steered toward arbitrary code execution.

With an EPSS score of 2.176% (84th percentile), this vulnerability sits in the upper band of expected near-term exploitation activity.

Root Cause

The defect is an integer overflow during length or count arithmetic on a value derived from the inbound IKEv2 payload header. When the computed size wraps around, the resulting allocation is far smaller than the data the parser then writes into it. This is a textbook [CWE-190] pattern in network protocol parsers that trust attacker-controlled length fields without bounds validation.

Attack Vector

Exploitation requires only network reachability to UDP ports 500 and 4500, the standard IKE and IKE-NAT-T ports. No credentials, user interaction, or pre-existing VPN tunnel is required. The attacker crafts a malformed IKEv2 packet with field values designed to trigger the integer wrap, then delivers it to the firewall's WAN interface. A single packet can crash the device; reliable code execution would require additional heap shaping primitives.

No public proof-of-concept code is currently available. Technical specifics are not disclosed in the vendor advisory.

Detection Methods for CVE-2024-40765

Indicators of Compromise

• Unexpected SonicOS reboots, crashes, or IPSec service restarts coinciding with inbound IKE traffic
• Malformed IKEv2 packets from untrusted sources on UDP/500 or UDP/4500
• Loss of VPN tunnel connectivity without corresponding configuration changes
• Anomalous outbound connections from the firewall management plane following an IKE crash event

Detection Strategies

• Monitor SonicOS system logs for repeated IPSec process failures, kernel panics, or unexpected reboot messages
• Deploy network intrusion detection signatures that flag oversized or malformed IKEv2 SA_INIT payloads
• Correlate firewall availability alerts with packet captures of inbound IKE traffic to identify the trigger source
• Track source IPs sending high volumes of IKE traffic to firewall WAN interfaces from outside expected VPN peer ranges

Monitoring Recommendations

• Forward SonicOS syslog to a centralized SIEM and alert on IPSec or IKE daemon termination events
• Capture full packet metadata for UDP/500 and UDP/4500 traffic to support post-incident analysis
• Baseline normal IKE peer IP addresses and alert on negotiation attempts from unknown sources
• Monitor firewall CPU, memory, and uptime metrics for sudden discontinuities indicative of crash-restart cycles

How to Mitigate CVE-2024-40765

Immediate Actions Required

• Apply the SonicOS firmware update referenced in SonicWall Advisory SNWLID-2024-0013 as the primary remediation
• Inventory all SonicWall appliances and confirm firmware versions against the vendor's fixed-release list
• Restrict IKE/IPSec exposure on internet-facing interfaces to known VPN peer IP addresses where operationally feasible
• Review firewall logs for prior crash events that may indicate exploitation attempts

Patch Information

SonicWall has released fixed SonicOS firmware versions documented in advisory SNWLID-2024-0013. Administrators should consult the SonicWall PSIRT advisory for version-specific upgrade paths and apply patches through the standard SonicOS firmware update process. Schedule maintenance windows and validate failover/HA configurations before upgrade.

Workarounds

• Disable IPSec VPN services on affected appliances if patching cannot be performed immediately and the service is not required
• Apply access control lists to limit UDP/500 and UDP/4500 traffic to known VPN peer addresses
• Place upstream filtering devices in front of the firewall to drop malformed IKEv2 traffic
• Enable High Availability pairs to reduce outage impact from DoS-triggered crashes during the patching window

# Example: restrict IKE traffic to known VPN peers using an upstream ACL
# Replace peer IPs with your authorized VPN endpoints
access-list IKE_FILTER permit udp host 203.0.113.10 any eq 500
access-list IKE_FILTER permit udp host 203.0.113.10 any eq 4500
access-list IKE_FILTER deny   udp any any eq 500
access-list IKE_FILTER deny   udp any any eq 4500
access-list IKE_FILTER permit ip any any