CVE-2002-0256 in NetDSL
Summary
by MITRE
The telnet port in Arescom NetDSL 1000 router allows remote attackers to cause a denial of service via a series of connections with long strings, which causes a large number of login failures and causes the telnet service to stop.
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Analysis
by VulDB Data Team • 09/02/2024
The CVE-2002-0256 vulnerability affects the telnet service implementation in Arescom NetDSL 1000 routers, representing a classic denial of service weakness that exploits poor input validation and connection handling mechanisms. This vulnerability specifically targets the telnet port which serves as a primary administrative interface for the device, making it a critical attack surface for remote adversaries seeking to disrupt network operations. The flaw manifests when attackers establish multiple telnet connections while simultaneously sending excessively long string inputs, creating a cascade of login failures that ultimately exhausts the service's resources and terminates the telnet daemon.
The technical implementation of this vulnerability stems from inadequate buffer management and authentication loop handling within the router's telnet service. When the system receives malformed input strings exceeding predefined length limits, the authentication mechanism fails to properly validate or truncate these inputs, leading to resource exhaustion during the login process. This behavior aligns with CWE-122, which describes buffer overflow vulnerabilities, and CWE-770, which covers excessive resource consumption. The router's failure to implement proper input sanitization and connection rate limiting creates an exploitable condition where legitimate users cannot access the service while attackers can systematically disable it through resource exhaustion attacks.
The operational impact of this vulnerability extends beyond simple service disruption, as it provides attackers with a reliable method to render network infrastructure inaccessible. Network administrators who rely on telnet for remote management face significant operational challenges when this service becomes unavailable, potentially forcing them to resort to physical access or alternative management protocols. The vulnerability also demonstrates poor security design principles that violate fundamental network security practices, as it fails to implement basic protection mechanisms such as connection throttling, input length validation, and automatic account lockout features. This weakness is particularly concerning in enterprise environments where router availability directly impacts network connectivity and business operations.
Mitigation strategies for CVE-2002-0256 should prioritize immediate implementation of network access controls and service hardening measures. Organizations must disable or restrict access to the telnet service through firewall rules, preferring secure alternatives such as SSH for remote administration. The router firmware should be updated to address the underlying implementation flaws, and administrators should implement connection rate limiting to prevent the exploitation pattern. Additionally, monitoring systems should be deployed to detect unusual connection patterns and login failure spikes that may indicate attempted exploitation. This vulnerability also highlights the importance of following ATT&CK framework tactics such as T1499 for network denial of service and T1078 for valid accounts usage, as attackers can leverage legitimate administrative access points to cause service disruption. Security teams should implement comprehensive patch management processes and regularly audit network device configurations to prevent similar vulnerabilities from persisting in other network infrastructure components.