CVE-2004-0040 in VPN-1
Summary
by MITRE
Stack-based buffer overflow in Check Point VPN-1 Server 4.1 through 4.1 SP6 and Check Point SecuRemote/SecureClient 4.1 through 4.1 build 4200 allows remote attackers to execute arbitrary code via an ISAKMP packet with a large Certificate Request packet.
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Analysis
by VulDB Data Team • 07/13/2025
The vulnerability described in CVE-2004-0040 represents a critical stack-based buffer overflow affecting Check Point VPN-1 Server versions 4.1 through 4.1 SP6 and Check Point SecuRemote/SecureClient 4.1 through build 4200. This flaw exists within the Internet Security Association and Key Management Protocol (ISAKMP) processing functionality, specifically when handling Certificate Request packets that exceed normal size parameters. The vulnerability stems from inadequate input validation and bounds checking within the ISAKMP packet handling routines, creating an exploitable condition where maliciously crafted packets can overwrite adjacent memory locations on the stack. The flaw operates at the network protocol level, making it particularly dangerous as it can be triggered remotely without requiring authentication or prior access to the system. This vulnerability directly maps to CWE-121 Stack-based Buffer Overflow, which is classified as a fundamental memory safety issue where data written to a buffer extends beyond the allocated stack space, potentially corrupting program execution flow. The attack vector involves sending a specially crafted ISAKMP packet containing an oversized Certificate Request field, which when processed by the vulnerable software causes the stack to overflow and overwrite critical memory segments including return addresses and function pointers.
The operational impact of this vulnerability extends beyond simple code execution to potentially enable complete system compromise and unauthorized access to protected networks. When successfully exploited, the buffer overflow allows remote attackers to inject and execute arbitrary code with the privileges of the affected service process, typically running with elevated system permissions. This capability enables attackers to establish persistent backdoors, escalate privileges, or launch further attacks against the internal network infrastructure. The vulnerability affects both server and client components of the Check Point security solution, creating potential attack paths through either endpoint. The exploitation process typically involves crafting an ISAKMP packet with a Certificate Request field that exceeds the expected buffer size, causing the stack corruption that leads to code execution. This vulnerability particularly impacts enterprise security infrastructures where VPN services are critical for remote access, making it a prime target for attackers seeking to gain unauthorized access to corporate networks. The attack scenario aligns with ATT&CK technique T1071.004 for Application Layer Protocol: DNS, though in this case the protocol is ISAKMP rather than DNS, and it also relates to T1059.001 for Command and Scripting Interpreter: PowerShell or Command Prompt, as the executed code often involves system command execution. The vulnerability's severity is compounded by the fact that ISAKMP is a fundamental protocol for establishing secure communications, making the attack surface particularly wide and impactful.
Mitigation strategies for CVE-2004-0040 should focus on immediate patching of affected systems, as Check Point released security updates addressing this specific vulnerability. Organizations must ensure all VPN-1 Server and SecuRemote/SecureClient installations are updated to versions containing the patched ISAKMP packet handling routines. Network segmentation and access controls should be implemented to limit exposure of vulnerable systems to untrusted networks, particularly restricting direct access to ISAKMP ports and services. The implementation of intrusion detection systems capable of identifying and blocking malformed ISAKMP packets can provide additional layers of defense. Regular security assessments and vulnerability scanning should be conducted to identify any remaining instances of the vulnerable software within the network infrastructure. System hardening practices including disabling unnecessary services, implementing proper input validation, and monitoring for unusual network traffic patterns can help detect potential exploitation attempts. Organizations should also consider implementing network access control measures that can filter out packets with suspiciously large Certificate Request fields, providing defense-in-depth against this specific attack pattern. The vulnerability demonstrates the importance of proper memory management practices and input validation in security-critical applications, aligning with industry best practices outlined in secure coding standards such as those promoted by the CERT/CC and the Open Web Application Security Project. Regular patch management programs should be established to ensure timely deployment of security updates, particularly for mission-critical infrastructure components like VPN servers that handle sensitive network communications.