CVE-2001-0710 in FreeBSD
Summary
by MITRE
NetBSD 1.5 and earlier and FreeBSD 4.3 and earlier allows a remote attacker to cause a denial of service by sending a large number of IP fragments to the machine, exhausting the mbuf pool.
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Analysis
by VulDB Data Team • 02/13/2017
The vulnerability described in CVE-2001-0710 represents a classic denial of service flaw affecting network operating systems that was prevalent in the early 2000s. This issue impacts NetBSD versions 1.5 and earlier, as well as FreeBSD versions 4.3 and earlier, demonstrating the widespread nature of memory management weaknesses in operating system kernels during that period. The flaw specifically targets the mbuf pool mechanism, which serves as a critical memory allocation system for network packet handling in these unix-like systems. When an attacker exploits this vulnerability, they can send an excessive volume of IP fragments to a target system, causing the mbuf pool to become exhausted and ultimately leading to system instability or complete service disruption.
The technical root cause of this vulnerability lies in insufficient validation and resource management within the IP fragment reassembly process. When systems receive fragmented IP packets, they must allocate mbuf structures to store and reassemble the fragments before delivering them to higher-level protocols. In the affected versions of NetBSD and FreeBSD, the implementation failed to properly limit the number of fragments that could be queued for reassembly or the total memory allocated for this purpose. This lack of resource control creates a scenario where an attacker can continuously send IP fragments that consume all available mbuf pool resources, effectively starving the system of memory needed for legitimate network operations. The vulnerability directly maps to CWE-400, which categorizes "Uncontrolled Resource Consumption" as a significant weakness in software systems, particularly in network protocol implementations.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise system availability and reliability. Network administrators and system operators would face challenges in maintaining network connectivity and service availability when their systems are subjected to such attacks. The effects manifest as complete denial of service conditions where legitimate network traffic cannot be processed due to the exhaustion of critical kernel memory resources. Systems may become unresponsive to network traffic, require manual intervention to recover, or experience complete system crashes. This vulnerability particularly affected network servers, routers, and firewalls that process large volumes of network traffic, making it a significant concern for infrastructure providers and enterprise networks. The attack vector is straightforward and requires minimal resources to execute, making it an attractive method for denial of service attacks.
Mitigation strategies for this vulnerability involve both immediate system patches and long-term architectural improvements. The primary solution requires updating to patched versions of NetBSD and FreeBSD where the mbuf pool management has been enhanced with proper resource limits and validation mechanisms. System administrators should implement rate limiting on IP fragment processing and configure appropriate mbuf pool size limits to prevent exhaustion. Network security measures such as firewall rules can be configured to limit the number of fragments allowed per connection or per time period. Additionally, implementing monitoring and alerting systems can help detect unusual fragment traffic patterns that may indicate an ongoing attack. Organizations should also consider implementing intrusion detection systems that can identify and block suspicious fragment traffic patterns. This vulnerability highlights the importance of proper resource management in kernel implementations and aligns with ATT&CK technique T1499, which covers "Network Denial of Service" attacks targeting system resources. The fix typically involves implementing bounded queues for fragment reassembly and proper memory accounting to prevent unbounded resource consumption.