CVE-2005-4276 in Versalink
Summary
by MITRE
Westell Versalink 327W allows remote attackers to cause a denial of service (device crash) via an IP packet with the same source and destination IPs and ports, and with the SYN flag set (aka LanD). NOTE: the provenance of this issue is unknown; the details are obtained solely from third party information.
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Analysis
by VulDB Data Team • 12/07/2024
The Westell Versalink 327W is a network device that serves as a broadband router and wireless access point, commonly deployed in residential and small office environments. This device operates as a critical network gateway component that handles incoming and outgoing network traffic, making it a prime target for exploitation. The vulnerability in question represents a specific weakness in the device's packet processing logic that can be leveraged by remote attackers to disrupt network services. The device's failure to properly validate incoming IP packets creates an opportunity for malicious actors to exploit a fundamental aspect of network communication protocols. The vulnerability specifically targets the TCP/IP stack implementation within the device's firmware, where improper handling of malformed packets leads to system instability.
The technical flaw manifests when the device receives an IP packet that contains identical source and destination IP addresses and port numbers, with the SYN flag specifically set in the TCP header. This particular packet configuration creates a condition where the device's network processing engine enters an infinite loop or encounters a memory corruption scenario. The LanD attack pattern exploits the device's failure to implement proper packet validation checks before processing incoming network traffic. The SYN flag indicates a connection request in TCP protocol, but when combined with identical source and destination fields, it creates an impossible state that the device cannot properly handle. This type of vulnerability falls under the category of malformed packet processing errors, which are commonly classified as CWE-129 and CWE-770 in the Common Weakness Enumeration system. The device's TCP stack implementation lacks proper input sanitization and validation mechanisms that would normally detect and reject such malformed packets.
The operational impact of this vulnerability is significant as it allows remote attackers to cause a complete denial of service condition that renders the entire network infrastructure unusable. When the device crashes or becomes unresponsive, all network services provided by the Westell Versalink 327W cease to function, affecting internet connectivity, wireless access, and any other network-dependent services. The attack can be executed from anywhere on the internet without requiring authentication or local network access, making it particularly dangerous for widespread exploitation. Network administrators may experience extended downtime while attempting to restore service, as the device typically requires a complete reboot to recover from the crash condition. The vulnerability can be exploited repeatedly, allowing attackers to maintain persistent disruption of network services. This type of attack pattern aligns with the tactics described in the MITRE ATT&CK framework under the T1498 technique for Network Denial of Service, where adversaries leverage weaknesses in network infrastructure to create persistent service interruptions.
Mitigation strategies for this vulnerability involve implementing network-level protections such as firewall rules that filter out packets with identical source and destination IP addresses and ports, effectively preventing the malformed packets from reaching the device. Network administrators should also consider applying firmware updates from Westell if available, though the age of this vulnerability suggests limited vendor support. The device should be isolated from untrusted networks or placed behind robust network segmentation controls to limit potential attack vectors. Additionally, implementing intrusion detection systems that can identify and alert on anomalous packet patterns can help detect exploitation attempts. Regular monitoring of network traffic for unusual patterns and implementing proper network access controls can further reduce the risk of successful exploitation. Organizations should also maintain backup network infrastructure and emergency procedures to quickly restore services in case of successful attack execution. The vulnerability demonstrates the importance of proper input validation and robust error handling in network infrastructure devices, as recommended by industry best practices for secure network design and implementation.