CVE-2005-4257 in BEFW11S4
Summary
by MITRE
Linksys WRT54GS and BEFW11S4 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 the BID.
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Analysis
by VulDB Data Team • 07/14/2018
The vulnerability described in CVE-2005-4257 represents a classic denial of service flaw affecting Linksys WRT54GS and BEFW11S4 wireless routers. This issue manifests when an attacker crafts a specific IP packet that contains identical source and destination IP addresses and port numbers, with the SYN flag explicitly set. The LAND attack technique exploits a fundamental flaw in how these network devices process incoming packets, creating a condition that leads to device instability and eventual system crash. The vulnerability specifically targets the TCP/IP stack implementation within the router firmware, where the device fails to properly handle packets with identical source and destination parameters.
The technical execution of this attack relies on the manipulation of TCP connection establishment protocols. When a router receives a packet with matching source and destination IP addresses and ports, the device's network processing engine becomes trapped in an infinite loop or encounters a memory corruption scenario. This occurs because the router's TCP stack implementation lacks proper validation of packet parameters, particularly when dealing with packets that exhibit the characteristics of a LAND attack. The SYN flag set in conjunction with identical source and destination addresses creates a condition where the router's connection handling logic becomes confused, leading to resource exhaustion or stack corruption that ultimately results in system crash. This vulnerability falls under the category of improper input validation as defined by CWE-20, specifically targeting network protocol handling mechanisms.
The operational impact of this vulnerability extends beyond simple service disruption, as it can render network infrastructure completely inaccessible to legitimate users. When exploited successfully, the LAND attack causes the affected routers to become unresponsive, requiring manual intervention for recovery through device reboot or firmware reset. Network administrators may experience extended downtime while troubleshooting the issue, particularly in environments where these routers serve as primary network gateways. The attack's remote nature means that unauthorized individuals can trigger the denial of service condition from outside the network perimeter, making it particularly dangerous for enterprise and home network deployments. This vulnerability represents a significant security weakness in the router's network stack implementation and can potentially be used as a precursor to more sophisticated attacks targeting the broader network infrastructure.
Mitigation strategies for CVE-2005-4257 focus on both network-level protection and device firmware updates. Network administrators should implement ingress filtering and packet validation mechanisms at network boundaries to block packets with identical source and destination addresses. The implementation of firewall rules that drop suspicious TCP packets with matching source and destination parameters provides an effective preventive measure. Additionally, firmware updates from Linksys addressing this specific vulnerability should be deployed immediately, as the issue stems from inadequate protocol handling within the router's software implementation. Network segmentation and monitoring systems can help detect anomalous packet patterns that may indicate attempted LAND attacks, providing early warning capabilities. The vulnerability demonstrates the critical importance of proper TCP stack implementation in network devices and aligns with ATT&CK technique T1499.001 for network denial of service attacks, emphasizing the need for robust input validation in network protocol processing components. Organizations should also consider implementing intrusion detection systems that can identify and alert on LAND attack patterns, as these attacks often precede more serious network compromise attempts.