CVE-2002-0886 in CBOS
Summary
by MITRE
Cisco DSL CPE devices running CBOS 2.4.4 and earlier allows remote attackers to cause a denial of service (hang or memory consumption) via (1) a large packet to the DHCP port, (2) a large packet to the Telnet port, or (3) a flood of large packets to the CPE, which causes the TCP/IP stack to consume large amounts of memory.
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Analysis
by VulDB Data Team • 09/06/2024
The vulnerability identified as CVE-2002-0886 affects Cisco DSL Customer Premises Equipment devices operating with CBOS version 2.4.4 or earlier, representing a significant denial of service weakness that can be exploited remotely by malicious actors. This flaw resides within the TCP/IP stack implementation of these network devices, specifically manifesting when the system receives malformed or oversized network packets through critical service ports. The vulnerability impacts the fundamental network communication capabilities of these devices, potentially rendering them completely non-functional and disrupting internet connectivity for end users. The affected devices are commonly deployed in residential and small business environments where reliable internet access is critical for daily operations.
The technical exploitation mechanism of this vulnerability involves sending oversized packets to specific network ports that the affected Cisco devices listen on for legitimate network services. When attackers send large packets to either the DHCP port or the Telnet port, or when they flood the device with multiple large packets, the TCP/IP stack within the CBOS operating system becomes overwhelmed. This condition causes the system to consume excessive memory resources, leading to either a complete system hang or gradual memory exhaustion that prevents normal operation. The root cause stems from inadequate input validation and memory management within the TCP/IP stack implementation, where the system fails to properly handle oversized packets that exceed normal network communication parameters. This vulnerability aligns with CWE-129, Input Validation, and CWE-772, Missing Release of Resource, as the system does not properly validate packet sizes or release memory resources after processing malformed input.
The operational impact of CVE-2002-0886 extends beyond simple service disruption to potentially compromise business continuity for organizations relying on these devices. When a Cisco DSL CPE device becomes unresponsive due to this vulnerability, end users lose internet connectivity, which can severely impact productivity in business environments or cause inconvenience in residential settings. The remote exploitation capability means that attackers do not require physical access to the device or network, making this vulnerability particularly dangerous as it can be exploited from anywhere on the internet. Organizations may experience cascading effects where multiple devices in a network are affected, potentially leading to widespread service outages. The vulnerability also represents a potential entry point for more sophisticated attacks, as the device's compromised state may make it easier for attackers to gain further access to the network infrastructure.
Mitigation strategies for CVE-2002-0886 should focus on both immediate protective measures and long-term system hardening approaches. The most effective immediate solution involves upgrading the CBOS software to version 2.4.5 or later, which contains patches addressing the memory consumption issues in the TCP/IP stack. Network administrators should also implement packet filtering rules at network boundaries to limit the size of packets allowed to reach the affected devices, particularly on ports 67 and 23 where DHCP and Telnet services operate respectively. Additionally, implementing rate limiting mechanisms can help prevent flood attacks from overwhelming the system's resources. Organizations should also consider deploying intrusion detection systems that can identify and alert on suspicious packet patterns that match the vulnerability characteristics. The remediation process should include comprehensive testing of updated firmware in controlled environments before widespread deployment, ensuring that the patches do not introduce compatibility issues with existing network configurations. This vulnerability demonstrates the importance of maintaining up-to-date network device firmware and implementing proper network segmentation to limit the potential impact of such exploits.