CVE-2005-3732 in IPsec-Tools
Summary
by MITRE
The Internet Key Exchange version 1 (IKEv1) implementation (isakmp_agg.c) in racoon in ipsec-tools before 0.6.3, when running in aggressive mode, allows remote attackers to cause a denial of service (null dereference and crash) via crafted IKE packets, as demonstrated by the PROTOS ISAKMP Test Suite for IKEv1.
Be aware that VulDB is the high quality source for vulnerability data.
Analysis
by VulDB Data Team • 06/29/2025
The vulnerability described in CVE-2005-3732 represents a critical denial of service flaw within the Internet Key Exchange version 1 implementation of the racoon IPsec daemon. This issue specifically affects ipsec-tools versions prior to 0.6.3 and manifests when the system operates in aggressive mode, a configuration that prioritizes faster key exchange but with reduced security guarantees. The vulnerability stems from improper handling of crafted IKE packets during the aggressive mode negotiation process, creating a condition where the isakmp_agg.c module fails to properly validate incoming packet structures before attempting to dereference pointers.
The technical exploitation of this vulnerability occurs through carefully constructed IKE packets that trigger a null pointer dereference within the racoon daemon's aggressive mode handler. When the system processes these malformed packets, the isakmp_agg.c component attempts to access memory locations that have not been properly initialized or validated, resulting in an immediate crash of the IPsec daemon. This behavior constitutes a classic null pointer dereference vulnerability, which is categorized under CWE-476 in the Common Weakness Enumeration framework. The crash occurs because the implementation fails to perform adequate input validation and error handling for the specific packet structures that can be generated during aggressive mode negotiations.
The operational impact of this vulnerability extends beyond simple service disruption, as it can be leveraged by remote attackers to systematically destabilize IPsec VPN services. When exploited successfully, the denial of service condition prevents legitimate users from establishing secure connections through the affected IPsec gateway, effectively rendering the VPN service unavailable. This type of vulnerability is particularly concerning in enterprise environments where IPsec VPNs serve as primary secure communication channels for remote access and site-to-site connections. The vulnerability's exploitation does not require authentication or special privileges, making it a significant threat vector that can be easily abused by anyone capable of sending network packets to the target system.
The attack vector for this vulnerability is particularly dangerous due to its remote nature and the fact that it can be triggered through normal network traffic without requiring any special access rights. The demonstration using the PROTOS ISAKMP Test Suite for IKEv1 indicates that the flaw is not theoretical but has been validated in real-world testing conditions, suggesting that attackers can readily develop exploit code. From an adversarial perspective, this vulnerability aligns with techniques described in the MITRE ATT&CK framework under the T1499 category for network denial of service attacks, where adversaries target network infrastructure services to disrupt legitimate access. Organizations using affected versions of racoon should immediately implement mitigations including updating to ipsec-tools 0.6.3 or later, implementing network access controls to restrict IKE traffic, and monitoring for suspicious packet patterns that might indicate exploitation attempts.
The root cause of this vulnerability highlights fundamental security weaknesses in the input validation and error handling mechanisms within the IPsec implementation. The flaw demonstrates the critical importance of proper resource management and defensive programming practices in security-critical software components. Organizations should consider implementing additional monitoring and intrusion detection measures to identify potential exploitation attempts, as well as establishing robust patch management procedures to ensure timely updates of security-critical components. The vulnerability also underscores the risks associated with aggressive mode in IKEv1, which while providing faster key exchange, introduces additional attack surface that must be carefully considered in security architecture decisions.