CVE-2004-0592 in Linux
Summary
by MITRE
The tcp_find_option function of the netfilter subsystem for IPv6 in the SUSE Linux 2.6.5 kernel with USAGI patches, when using iptables and TCP options rules, allows remote attackers to cause a denial of service (CPU consumption by infinite loop) via a large option length that produces a negative integer after a casting operation to the char type, a similar flaw to CVE-2004-0626.
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Analysis
by VulDB Data Team • 03/22/2018
The vulnerability identified as CVE-2004-0592 represents a critical flaw in the network packet processing subsystem of the Linux kernel, specifically within the netfilter framework that handles IPv6 traffic. This issue affects SUSE Linux distributions running kernel version 2.6.5 with USAGI patches, which are modifications designed to enhance IPv6 support in the Linux kernel. The vulnerability manifests in the tcp_find_option function, which is responsible for parsing TCP options within network packets. When iptables rules are configured to process TCP options, this function becomes susceptible to exploitation through malformed packet construction.
The technical root cause of this vulnerability stems from improper handling of integer casting operations within the tcp_find_option function. When processing TCP options with unusually large length values, the system performs a casting operation to the char data type, which can result in negative integer values. This casting behavior creates a condition where the loop counter becomes negative, causing the function to enter an infinite loop that consumes excessive CPU resources. The vulnerability is particularly dangerous because it operates at the kernel level, where malicious actors can exploit it without requiring elevated privileges, and the resulting denial of service can severely impact network availability and system performance.
The operational impact of this vulnerability extends beyond simple service disruption, as it can be leveraged by remote attackers to perform sustained denial of service attacks against targeted systems. When exploited, the infinite loop consumes CPU cycles continuously, potentially leading to system instability, resource exhaustion, and complete service unavailability for legitimate users. The vulnerability's similarity to CVE-2004-0626 demonstrates a pattern of integer overflow issues within the kernel's network processing code, indicating that this was part of a broader class of flaws affecting TCP option handling. This type of vulnerability falls under the Common Weakness Enumeration category CWE-191, which specifically addresses integer underflow conditions, and aligns with ATT&CK technique T1498 for network denial of service attacks.
Mitigation strategies for CVE-2004-0592 require immediate system updates and configuration changes to prevent exploitation. The most effective approach involves applying kernel patches that correct the integer casting behavior in the tcp_find_option function, ensuring that option length values are properly validated before casting operations occur. System administrators should also implement iptables rules that limit the processing of TCP options or drop packets with suspicious option lengths. Additionally, monitoring network traffic for unusual patterns of TCP option processing can help detect potential exploitation attempts. The vulnerability highlights the importance of thorough input validation in kernel space operations and demonstrates how seemingly minor issues in data type handling can result in significant security implications. Organizations should also consider implementing network segmentation and rate limiting to reduce the impact of such attacks and ensure that critical services remain available even when under attack.