CVE-2002-0574 in FreeBSD
Summary
by MITRE
Memory leak in FreeBSD 4.5 and earlier allows remote attackers to cause a denial of service (memory exhaustion) via ICMP echo packets that trigger a bug in ip_output() in which the reference count for a routing table entry is not decremented, which prevents the entry from being removed.
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Analysis
by VulDB Data Team • 02/11/2017
The vulnerability identified as CVE-2002-0574 represents a critical memory management flaw in FreeBSD operating systems version 4.5 and earlier. This issue manifests as a memory leak within the internet protocol output function known as ip_output() which is responsible for processing outgoing network packets. The flaw specifically affects the reference counting mechanism used to manage routing table entries, creating a condition where memory allocated for routing information becomes permanently inaccessible due to improper reference count management.
The technical implementation of this vulnerability occurs when ICMP echo packets are processed by the kernel's networking stack. During normal operation, when a routing table entry is accessed, its reference count should increment to indicate active usage and decrement when the entry is no longer needed. However, in the affected FreeBSD versions, the ip_output() function fails to properly decrement the reference count for routing table entries when processing certain ICMP echo packets. This reference count anomaly prevents the kernel from properly freeing the memory associated with these routing entries, leading to progressive memory consumption over time.
The operational impact of this vulnerability is significant as it enables remote attackers to perform denial of service attacks against FreeBSD systems. By sending carefully crafted ICMP echo packets to a target system, an attacker can repeatedly trigger the memory leak condition, causing the system's available memory to gradually deplete. As memory becomes exhausted, the system's performance deteriorates substantially, eventually leading to complete system unresponsiveness or crash. The vulnerability is particularly dangerous because it requires minimal resources to exploit and can be executed remotely without authentication, making it an attractive target for automated attack tools.
This memory leak vulnerability aligns with CWE-401, which specifically addresses improper handling of memory allocation and deallocation in software systems. The flaw demonstrates poor resource management practices that violate fundamental principles of memory safety and system stability. From an attack framework perspective, this vulnerability could be categorized under ATT&CK technique T1499.004, which covers network denial of service attacks. The vulnerability's remote exploitability and ability to cause system-wide memory exhaustion make it particularly effective for disrupting network services and can be combined with other attack vectors to create more sophisticated compromise scenarios.
The recommended mitigations for this vulnerability include immediate deployment of FreeBSD security patches that correct the reference counting logic in the ip_output() function. System administrators should prioritize updating to FreeBSD versions 4.6 and later where this issue has been resolved through proper implementation of routing table entry reference counting. Additionally, network administrators can implement traffic filtering rules to limit ICMP echo packet processing or reduce the rate of such packets entering the system. Monitoring for unusual memory consumption patterns and implementing automated alerting systems can help detect exploitation attempts before they cause significant system impact. The vulnerability serves as a critical reminder of the importance of proper resource management in kernel-level code and demonstrates how seemingly minor implementation flaws can result in severe system stability issues.