CVE-2000-0181 in Firewall-1
Summary
by MITRE
Firewall-1 3.0 and 4.0 leaks packets with private IP address information, which could allow remote attackers to determine the real IP address of the host that is making the connection.
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Analysis
by VulDB Data Team • 04/21/2026
The vulnerability identified as CVE-2000-0181 affects Check Point Firewall-1 versions 3.0 and 4.0, representing a significant security flaw in network perimeter protection systems. This issue stems from improper handling of packet processing within the firewall's network address translation and packet filtering mechanisms, creating an information disclosure vulnerability that directly impacts network security posture.
The technical flaw manifests when Firewall-1 systems process packets containing private IP addresses, particularly in scenarios involving network address translation or connection tracking. The system fails to properly sanitize or mask these private IP addresses during packet processing, resulting in the leakage of internal network addressing information to external parties. This occurs because the firewall's packet handling routines do not adequately strip or obfuscate private IP address information that should remain internal to the network infrastructure.
From an operational impact perspective, this vulnerability enables remote attackers to conduct reconnaissance activities that would otherwise be blocked by proper firewall configuration. The leaked private IP address information provides attackers with crucial network topology details, potentially revealing internal network structures, host configurations, and connection patterns. This information leakage significantly weakens the security boundary that firewalls are designed to maintain, as it undermines the fundamental principle of network address hiding and internal network protection that organizations rely upon for security.
The vulnerability aligns with CWE-200, which addresses information exposure, and represents a specific implementation flaw in network security device processing. From an ATT&CK framework perspective, this weakness maps to techniques involving reconnaissance and information gathering, specifically T1590 for reconnaissance and T1592 for reconnaissance using network sniffers or packet capture tools. The ability to determine real IP addresses through packet leakage directly supports adversarial activities that would typically require more sophisticated or direct access methods.
Organizations should implement immediate mitigations including updating to patched versions of Firewall-1, configuring proper packet filtering rules to prevent private address leakage, and conducting comprehensive network security assessments to identify potential exploitation of this vulnerability. Additionally, implementing network segmentation, using additional layers of protection, and monitoring for unusual packet patterns can help detect and prevent exploitation attempts. The vulnerability underscores the critical importance of proper packet handling in security appliances and demonstrates how seemingly minor implementation flaws can create significant security risks in network infrastructure protection systems.