CVE-2004-0911 in netkit
Summary
by MITRE
telnetd for netkit 0.17 and earlier, and possibly other versions, on Debian GNU/Linux allows remote attackers to cause a denial of service (free of an invalid pointer), a different vulnerability than CVE-2001-0554.
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Analysis
by VulDB Data Team • 06/02/2019
The vulnerability identified as CVE-2004-0911 affects telnetd implementations within netkit version 0.17 and earlier, as well as potentially other affected versions running on Debian GNU/Linux systems. This represents a critical security flaw that enables remote attackers to exploit a memory management issue within the telnet daemon service. The vulnerability specifically manifests as a denial of service condition caused by the improper handling of invalid pointers during the telnet protocol processing, which differs from the previously documented CVE-2001-0554 that addressed similar but distinct memory corruption issues.
The technical flaw stems from inadequate input validation and memory management within the telnetd service when processing malformed network requests or specific telnet protocol sequences. When remote attackers send carefully crafted telnet commands or establish connections with malformed parameters, the service attempts to free memory locations that either do not exist or have already been deallocated, resulting in invalid pointer dereferences. This memory corruption condition typically leads to the telnetd process crashing and terminating unexpectedly, thereby disrupting legitimate user access to the system through telnet services. The vulnerability operates at the application layer and leverages the inherent design weaknesses in how the telnet protocol is implemented within the netkit framework.
The operational impact of this vulnerability extends beyond simple service disruption as it creates potential opportunities for attackers to exploit system availability. When the telnetd service becomes unavailable due to the denial of service condition, legitimate users lose access to remote system administration capabilities, which can significantly impact system management and maintenance operations. Organizations relying on telnet for remote access may experience service interruptions that could affect critical infrastructure management, particularly in environments where alternative secure remote access methods are not readily available or properly configured. The vulnerability's remote nature means that attackers can exploit it without requiring local system access or authentication credentials.
Mitigation strategies for CVE-2004-0911 should prioritize immediate system updates and patches from Debian security repositories to address the specific memory management flaws in netkit versions. System administrators should implement network-level restrictions to limit telnet service exposure, including firewall rules that restrict access to telnet ports from trusted networks only. The recommended approach involves upgrading to patched versions of netkit that contain proper pointer validation and memory handling mechanisms, which aligns with industry standards for secure software development practices. Additionally, organizations should consider implementing alternative secure remote access protocols such as ssh, which provide better security controls and are less susceptible to the memory corruption vulnerabilities present in traditional telnet implementations. This vulnerability demonstrates the importance of proper memory management in network services and highlights the need for robust input validation mechanisms that prevent invalid pointer operations. The issue relates to CWE-476 which addresses null pointer dereference conditions, and may overlap with ATT&CK techniques related to denial of service and privilege escalation through service disruption. Organizations should conduct thorough vulnerability assessments to identify all systems running affected telnetd versions and implement comprehensive monitoring to detect potential exploitation attempts.