CVE-2002-0704 in Netfilter
Summary
by MITRE
The Network Address Translation (NAT) capability for Netfilter ("iptables") 1.2.6a and earlier leaks translated IP addresses in ICMP error messages.
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Analysis
by VulDB Data Team • 10/25/2024
The vulnerability described in CVE-2002-0704 represents a significant security flaw in the Netfilter framework's Network Address Translation implementation within Linux kernel versions 1.2.6a and earlier. This issue specifically affects the iptables firewall rules system that provides network address translation capabilities for Linux-based firewalls and routers. The vulnerability stems from improper handling of ICMP error messages generated during network traffic translation processes, creating a potential information disclosure risk that could compromise network security posture.
The technical flaw occurs when NAT translates IP addresses for packets passing through the firewall, but fails to properly sanitize ICMP error messages that may contain the original translated addresses. During normal network operations, when packets encounter issues such as port unreachability or network unreachable conditions, the system generates ICMP error messages to notify the originating host. In vulnerable versions of Netfilter, these ICMP error messages retain information about the translated IP addresses, effectively leaking internal network addressing information to external parties. This behavior violates fundamental security principles by exposing private network topology details that should remain concealed from external observers.
The operational impact of this vulnerability extends beyond simple information disclosure, as it provides attackers with valuable reconnaissance data that can be used to map internal network structures and identify potential attack vectors. When an external attacker sends traffic to a host behind a NAT firewall, and that traffic generates ICMP errors, the translated internal IP addresses become visible in the error messages. This leakage can reveal subnet boundaries, internal host configurations, and network architecture details that would otherwise remain hidden. The vulnerability is particularly concerning in environments where NAT is used for security purposes, as it undermines the very purpose of address translation by exposing the underlying network structure.
This vulnerability aligns with CWE-200, which addresses "Information Exposure," and represents a classic case of improper information sanitization in network protocol handling. The flaw demonstrates weaknesses in the principle of least privilege and information hiding that are fundamental to secure network design. From an ATT&CK framework perspective, this vulnerability enables threat actors to perform reconnaissance activities under technique T1046 Network Service Scanning and T1082 System Information Discovery, as the leaked information can be used to build detailed network maps and identify potential targets within the internal network infrastructure.
Mitigation strategies for CVE-2002-0704 involve upgrading to Netfilter versions 1.2.7 and later, where the issue has been addressed through proper ICMP message handling and IP address sanitization. System administrators should also implement additional network security measures such as restricting ICMP traffic at firewall levels, implementing proper access control lists, and conducting regular security audits of network infrastructure. Organizations using legacy systems that cannot be immediately upgraded should consider implementing network segmentation and additional monitoring to detect and respond to potential exploitation attempts. The fix implemented in newer versions ensures that ICMP error messages generated during NAT operations properly mask or remove translated addresses, preventing the information leakage that previously occurred.