CVE-1999-0675 in Firewall-1
Summary
by MITRE
Check Point FireWall-1 can be subjected to a denial of service via UDP packets that are sent through VPN-1 to port 0 of a host.
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Analysis
by VulDB Data Team • 04/19/2026
The vulnerability described in CVE-1999-0675 represents a critical denial of service weakness within Check Point FireWall-1 security infrastructure. This flaw specifically affects the VPN-1 implementation that operates as part of the broader Check Point security solution suite. The vulnerability manifests when the system receives specially crafted UDP packets that are directed to port 0 on target hosts within the network protected by the firewall. This particular configuration creates an exploitable condition that can disrupt normal network operations and compromise the availability of services.
The technical mechanism behind this vulnerability involves the improper handling of UDP packets with destination port 0 by the FireWall-1 software. In standard network protocols, port 0 is considered invalid and should not be used for legitimate communication. However, the FireWall-1 implementation fails to properly validate or reject these malformed packets, leading to system instability. When such packets are processed through the VPN-1 component, the firewall engine encounters difficulties in parsing the packet structure, which can result in system crashes or complete service disruption. This behavior aligns with CWE-122, which addresses buffer overflow conditions that occur when data exceeds allocated buffer space, though the specific manifestation here involves improper input validation rather than traditional buffer overflows.
The operational impact of this vulnerability extends beyond simple service interruption to potentially compromise the entire security infrastructure of organizations relying on Check Point FireWall-1. When exploited, the denial of service condition can render the firewall ineffective, leaving networks exposed to other threats while the security appliance is offline. This creates a dangerous scenario where network administrators may be unaware of the compromise, as the system simply becomes unresponsive rather than generating explicit security alerts. The vulnerability particularly affects environments where VPN services are actively utilized, as the exploitation requires packets to traverse the VPN-1 component, making it more prevalent in remote access scenarios.
Organizations with affected systems should prioritize immediate mitigation strategies to protect their network infrastructure. The primary recommendation involves implementing packet filtering rules that block UDP traffic destined for port 0, effectively preventing the vulnerable condition from being triggered. Additionally, network administrators should consider upgrading to patched versions of FireWall-1 software that properly validate incoming packet headers and reject malformed UDP traffic. This vulnerability demonstrates the importance of proper input validation in network security appliances, as highlighted in ATT&CK technique T1499.002 for network denial of service attacks. The incident also underscores the necessity of regular security updates and the potential for seemingly benign protocol behaviors to create critical security weaknesses in complex network infrastructure components.
The broader implications of this vulnerability extend to network security architecture design principles, particularly regarding the robustness of security appliances under adversarial conditions. This weakness illustrates how protocol implementations can create unexpected attack vectors, even when the underlying protocols appear to be functioning correctly. Security professionals should implement comprehensive monitoring solutions to detect unusual packet patterns and establish incident response procedures that account for potential denial of service conditions in critical network infrastructure components. The vulnerability serves as a reminder of the importance of thorough security testing, including protocol compliance verification and edge case handling, particularly in systems that operate as gateways for network traffic.