CVE-2000-0804 in Firewall-1
Summary
by MITRE
Check Point VPN-1/FireWall-1 4.1 and earlier allows remote attackers to bypass the directionality check via fragmented TCP connection requests or reopening closed TCP connection requests, aka "One-way Connection Enforcement Bypass."
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Analysis
by VulDB Data Team • 05/27/2018
The vulnerability identified as CVE-2000-0804 affects Check Point VPN-1/FireWall-1 version 4.1 and earlier implementations, representing a critical flaw in network security enforcement mechanisms. This vulnerability specifically targets the directionality checking functionality that is fundamental to proper firewall operation and connection management. The issue stems from how the system handles TCP connection requests, particularly when these requests are fragmented or when closed connections are reopened, creating opportunities for malicious actors to circumvent established security policies.
The technical flaw manifests in the improper handling of TCP connection state management within the firewall's enforcement engine. When TCP packets arrive in fragmented form or when previously closed connections are re-established, the system fails to properly validate the directionality of these connections against its established security policies. This weakness allows attackers to exploit the gap in connection validation logic, effectively bypassing the one-way connection enforcement mechanism that should prevent unauthorized traffic flows. The vulnerability operates at the network protocol level, specifically targeting the TCP/IP stack implementation within the firewall's packet processing pipeline.
From an operational impact perspective, this vulnerability creates significant security risks for organizations relying on Check Point Firewall-1 versions 4.1 and earlier. Attackers can exploit this flaw to establish unauthorized communication channels that would normally be blocked by the firewall's directionality enforcement rules. This bypass capability undermines the fundamental security model of the firewall, potentially allowing malicious traffic to traverse network boundaries without proper authorization. The vulnerability is particularly dangerous because it operates at the network layer, making it difficult to detect through traditional application-level monitoring and potentially enabling more sophisticated attacks such as port scanning, data exfiltration, or lateral movement within the network.
The vulnerability maps to CWE-119, which addresses "Improper Restriction of Operations within the Bounds of a Memory Buffer" and CWE-284, which covers "Improper Access Control" in firewall implementations. From an ATT&CK framework perspective, this vulnerability aligns with techniques such as T1046 for Network Service Scanning and T1566 for Phishing, as it enables attackers to establish unauthorized network connections that bypass security controls. The flaw also relates to T1071.004 for Application Layer Protocol: DNS and T1571 for Application Layer Protocol: Web Protocols, as attackers can exploit the bypassed connections to establish malicious communication channels. Organizations should implement immediate mitigations including upgrading to patched versions of Check Point Firewall-1, implementing additional network segmentation, and deploying intrusion detection systems to monitor for anomalous TCP connection patterns that might indicate exploitation attempts.
The root cause of this vulnerability lies in inadequate state management and validation of TCP connection requests within the firewall's enforcement engine. The system's failure to properly track connection directionality when dealing with fragmented packets or connection reopens creates a persistent security gap that attackers can consistently exploit. This flaw represents a fundamental weakness in the firewall's packet processing logic and demonstrates the importance of proper stateful inspection in network security appliances. The vulnerability's persistence across multiple connection scenarios makes it particularly challenging to defend against through conventional means, requiring comprehensive system updates and potentially additional security controls to maintain network integrity. Organizations should prioritize patch management and security assessments to ensure their firewall implementations properly handle all TCP connection states and packet fragmentation scenarios, as this vulnerability represents a critical threat to network security posture and compliance requirements.