CVE-2002-1431 in F5D5230-4 Cable Dsl Gateway Router
Summary
by MITRE
Belkin F5D5230-4 4-Port Cable/DSL Gateway Router 1.20.000 modifies the source IP address of internal packets to that of the router s external interface when forwarding a request from an internal host to an internal web server, which allows remote attackers to hide which host is being used to access the web server.
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Analysis
by VulDB Data Team • 07/01/2024
This vulnerability exists in the Belkin F5D5230-4 4-Port Cable/DSL Gateway Router firmware version 1.20.000 where the device fails to properly maintain source IP address integrity during packet forwarding operations. The flaw occurs when internal hosts attempt to access internal web servers through the router's NAT functionality, creating a specific scenario where the router incorrectly modifies the source IP address of packets originating from internal networks. This behavior represents a fundamental breakdown in network address translation mechanisms that should preserve the original source IP addresses of internal hosts while only modifying destination addresses for external communications.
The technical implementation of this vulnerability stems from improper NAT handling within the router's packet processing pipeline. When an internal host sends a request to an internal web server, the router should maintain the original source IP address to ensure proper network logging and security monitoring. However, this particular firmware version incorrectly rewrites the source IP address to match the router's external interface IP address, effectively masking the true origin of network requests. This modification occurs during the forwarding process and affects only internal-to-internal communications where the destination server is also within the local network, creating a false impression that external hosts are making the requests.
The operational impact of this vulnerability creates significant security implications for network administrators and security monitoring systems. Network intrusion detection systems and security information and event management platforms rely on accurate source IP address information to identify potential threats and track network activity patterns. When the router modifies source IP addresses, it creates false attribution that can obscure legitimate network behavior and hinder forensic investigations. Attackers can exploit this behavior to conduct reconnaissance activities while avoiding detection, as their internal host addresses are hidden behind the router's external IP address, making it appear as though external systems are accessing internal resources.
This vulnerability aligns with CWE-1286 which describes improper handling of network address translation and address manipulation in network devices. The flaw also corresponds to ATT&CK technique T1018 which involves valid accounts and network discovery, as it enables attackers to obscure their true network positions while conducting internal reconnaissance. The behavior creates a false sense of security for network monitoring systems and can be exploited to bypass network access controls that rely on source IP address validation. Organizations using this router configuration may experience difficulties in maintaining accurate network audit trails and could be vulnerable to attacks that rely on source IP address manipulation for evasion purposes.
The recommended mitigations for this vulnerability include immediate firmware updates from Belkin to address the NAT implementation flaw, network segmentation to isolate critical internal servers from general internal networks, and implementation of additional network monitoring controls that can detect anomalous source IP address patterns. Network administrators should also consider deploying network-based intrusion detection systems that can identify unusual traffic patterns consistent with source address manipulation. Regular network audits should verify that NAT configurations maintain proper source IP address integrity, and organizations should implement comprehensive logging solutions that capture both original and modified IP address information for forensic analysis purposes.