CVE-2003-1591 in NetWare
Summary
by MITRE
NWFTPD.nlm in the FTP server in Novell NetWare 6.0 before SP4 and 6.5 before SP1 allows user-assisted remote attackers to cause a denial of service (console hang) via a large number of FTP sessions, which are not properly handled during an NLM unload.
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Analysis
by VulDB Data Team • 05/04/2026
The vulnerability identified as CVE-2003-1591 affects the NWFTPD.nlm FTP server module in Novell NetWare 6.0 and 6.5 systems prior to their respective service packs. This represents a classic resource exhaustion attack vector that exploits improper session management during module unloading operations. The flaw specifically manifests when a large number of concurrent FTP sessions are established and subsequently terminated, leading to a critical system state where the console becomes unresponsive. This vulnerability operates under the principle of insufficient resource management as classified by CWE-400, where the system fails to properly handle the cleanup of allocated resources during module shutdown sequences.
The technical execution of this vulnerability relies on user-assisted remote exploitation, meaning that an attacker must first establish legitimate FTP connections to the target system before initiating the denial of service attack. During normal operation, each FTP session consumes system resources including memory allocations and file handles. However, when the NWFTPD.nlm module undergoes unloading or shutdown procedures, the system fails to properly release all allocated resources from the numerous concurrent sessions, causing a cascade of resource management failures. This results in a complete console hang where the system becomes unresponsive to all console commands and operations.
The operational impact of CVE-2003-1591 extends beyond simple service disruption as it fundamentally compromises system availability and reliability. Organizations relying on Novell NetWare 6.0 and 6.5 servers for critical file transfer operations face significant business continuity risks when this vulnerability is exploited. The console hang condition prevents administrators from performing essential maintenance tasks, monitoring system health, or responding to other security incidents, creating a cascading effect that can severely impact network operations. This vulnerability aligns with ATT&CK technique T1499.004 for network denial of service attacks and represents a critical weakness in the system's resource management and module lifecycle handling capabilities.
Mitigation strategies for this vulnerability require immediate implementation of Novell's official service packs, specifically SP4 for NetWare 6.0 and SP1 for NetWare 6.5, which contain the necessary code fixes for proper session cleanup during module unloading. Network administrators should also implement connection rate limiting and session monitoring to detect and prevent exploitation attempts before they can cause system-wide disruption. Additionally, implementing redundant console access methods and automated failover procedures can help maintain operational continuity during potential exploitation events. The vulnerability demonstrates the critical importance of proper resource management in server applications and serves as a reminder of the necessity for comprehensive testing of module lifecycle operations in enterprise operating systems.