CVE-2003-1250 in 5861 DSL Router
Summary
by MITRE
Efficient Networks 5861 DSL router, when running firmware 5.3.80 configured to block incoming TCP SYN, packets allows remote attackers to cause a denial of service (crash) via a flood of TCP SYN packets to the WAN interface using a port scanner such as nmap.
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Analysis
by VulDB Data Team • 05/26/2019
The vulnerability identified as CVE-2003-1250 affects the Efficient Networks 5861 DSL router running firmware version 5.3.80 with specific TCP SYN packet blocking configuration. This represents a significant denial of service weakness that directly impacts network availability and operational continuity. The router's implementation of TCP SYN packet filtering creates a critical flaw in its packet processing logic, where the device fails to properly handle high-volume TCP SYN flood attacks. The vulnerability specifically manifests when the router's firewall rules are configured to block incoming TCP SYN packets, which is a common security practice to prevent certain types of network attacks. However, this particular implementation does not adequately protect against resource exhaustion scenarios that occur when attackers flood the WAN interface with SYN packets from various source ports.
The technical flaw stems from inadequate input validation and resource management within the router's network processing stack. When the router receives a flood of TCP SYN packets, its processing capabilities become overwhelmed, leading to system instability and eventual crash conditions. This behavior aligns with CWE-400, which describes the weakness of uncontrolled resource consumption, specifically manifesting as a denial of service through resource exhaustion. The vulnerability operates at the network protocol level where the router's TCP stack implementation fails to properly rate-limit or queue incoming SYN packets, causing memory allocation failures or process scheduling issues. The attack vector is particularly effective because it leverages legitimate network protocols and common scanning tools like nmap, making it difficult to distinguish between malicious activity and normal network reconnaissance.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise network infrastructure reliability and business continuity. Organizations relying on this router configuration face significant risks of unauthorized service disruption, particularly during peak network usage periods when the device is already under stress. The vulnerability enables attackers to cause complete system outages without requiring authentication or advanced technical skills, making it a particularly dangerous weakness in network security infrastructure. Network administrators may experience extended downtime while attempting to restore service, and the impact can cascade to dependent systems that rely on the router for internet connectivity and traffic filtering. This vulnerability directly violates principles of availability in the CIA triad and represents a critical weakness in network device security that can be exploited by both amateur and sophisticated attackers.
Mitigation strategies for CVE-2003-1250 should focus on immediate firmware updates from Efficient Networks, which would address the underlying packet processing flaws. Network administrators should implement additional protective measures such as rate limiting at the network perimeter, intrusion detection system deployment, and traffic shaping policies that prevent SYN flood attacks from reaching the vulnerable device. The implementation of SYN cookies or other TCP stack hardening techniques can provide additional protection against this specific attack pattern. Organizations should also consider network segmentation to isolate critical infrastructure from potentially vulnerable devices and establish monitoring protocols to detect unusual traffic patterns that may indicate an ongoing attack. According to ATT&CK framework category T1498, this vulnerability maps to the 'Network Denial of Service' technique, while the exploitation methods align with T1595 for reconnaissance activities and T1071 for application layer protocol usage. The vulnerability demonstrates the importance of proper input validation and resource management in network security devices, as outlined in industry standards for embedded system security and secure coding practices.