CVE-2006-1067 in WRT54G V5
Summary
by MITRE
Linksys WRT54G routers version 5 (running VXWorks) allow remote attackers to cause a denial of service by sending a malformed DCC SEND string to an IRC channel, which causes an IRC connection reset, possibly related to the masquerading code for NAT environments, and as demonstrated via (1) a DCC SEND with a single long argument, or (2) a DCC SEND with IP, port, and filesize arguments with a 0 value.
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Analysis
by VulDB Data Team • 09/10/2017
The CVE-2006-1067 vulnerability affects Linksys WRT54G routers running version 5 with VXWorks firmware, representing a significant denial of service weakness in embedded networking equipment. This vulnerability specifically targets the router's IRC client implementation within its web interface, where the device attempts to handle DCC SEND commands from IRC channels. The flaw manifests when the router receives malformed DCC SEND strings that trigger unexpected behavior in the NAT masquerading code, which is responsible for managing network address translation and port forwarding for connected devices. The vulnerability exploits the router's handling of IRC protocol communications, particularly focusing on the DCC SEND command structure that is used for file transfers in IRC networks. The attack vectors demonstrate two distinct methods of exploitation where the malformed data causes the router to reset its IRC connection, effectively disrupting the device's ability to maintain stable network communications and potentially affecting all connected devices relying on the router's services.
The technical implementation of this vulnerability stems from inadequate input validation within the router's VXWorks-based firmware, specifically in how it processes DCC SEND arguments received through IRC protocol connections. The masquerading code responsible for NAT functionality contains a buffer overflow or memory corruption issue when processing the argument structure of DCC SEND commands. When attackers send a single long argument or provide IP, port, and filesize arguments with zero values, the router's processing logic fails to properly validate the input parameters, causing a stack overflow or memory corruption that results in an immediate reset of the IRC connection. This behavior aligns with common CWE classifications related to buffer overflows and improper input validation, specifically CWE-121 for buffer overflow conditions and CWE-20 for improper input validation. The vulnerability represents a classic example of how embedded systems can be exploited through protocol parsing flaws, where the router's firmware fails to properly sanitize external inputs from network communications.
The operational impact of this vulnerability extends beyond simple service disruption, as it can affect network availability and potentially compromise the security posture of devices relying on the affected router. When the router resets its IRC connection, it can cause cascading effects throughout the network, particularly if the device is configured to use the router's IRC client for monitoring or communication purposes. The vulnerability affects all devices connected to the network as the router's service interruption impacts the entire local network segment. In practical terms, this means that legitimate network users may experience intermittent connectivity issues, DNS resolution failures, or complete network outages depending on how the router's services are configured. The attack can be executed remotely without requiring authentication, making it particularly dangerous as any external attacker can potentially trigger the denial of service condition. This vulnerability demonstrates the importance of proper input validation in embedded systems and highlights how seemingly benign protocol implementations can create significant security weaknesses.
Mitigation strategies for this vulnerability require immediate firmware updates from Linksys or third-party firmware developers, as the flaw exists within the core firmware implementation of the router's VXWorks operating system. Network administrators should implement network segmentation and access control measures to limit exposure to potential attackers, particularly by blocking IRC protocol traffic at network boundaries. The recommended approach includes disabling IRC client functionality on the router when not required, as well as implementing intrusion detection systems that can monitor for malformed DCC SEND commands. Organizations should also consider deploying network monitoring tools that can detect unusual patterns of IRC protocol traffic that may indicate exploitation attempts. From an ATT&CK framework perspective, this vulnerability maps to techniques involving denial of service through protocol manipulation and remote code execution through buffer overflows, specifically using T1499.004 for network denial of service and T1059.007 for command and scripting interpreter. The vulnerability highlights the necessity of secure coding practices in embedded systems development and proper security testing of protocol implementations before deployment in production environments.