CVE-2000-1246 in NetWare
Summary
by MITRE
NWFTPD.nlm before 5.01o in the FTP server in Novell NetWare 5.1 SP3 allows remote authenticated users to cause a denial of service (abend) by sending an RNTO command after a failed RNFR command.
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Analysis
by VulDB Data Team • 05/04/2026
The vulnerability described in CVE-2000-1246 represents a classic denial of service flaw within the Novell NetWare 5.1 SP3 FTP server implementation. This issue specifically affects the NWFTPD.nlm module, which serves as the core FTP daemon responsible for handling file transfer protocol operations within the NetWare environment. The vulnerability manifests when an authenticated remote user exploits a particular sequence of commands that triggers an abnormal system termination or abend condition. The flaw exists in the protocol handling logic where the server fails to properly validate or manage the state transitions between different FTP commands, particularly when dealing with rename operations.
The technical execution of this vulnerability relies on the specific command sequence involving RNFR (rename from) and RNTO (rename to) commands within the FTP protocol. When a user first attempts a rename operation using RNFR and the operation fails for any reason, the server maintains an inconsistent internal state. Subsequently, if the same authenticated user sends an RNTO command, the FTP server's implementation lacks proper error handling or state validation mechanisms. This results in the server entering an undefined state that ultimately leads to a system crash or abend, effectively rendering the FTP service unavailable to legitimate users. The vulnerability is particularly concerning because it requires only authenticated access, meaning that any user with valid credentials can potentially disrupt service.
The operational impact of this vulnerability extends beyond simple service disruption as it can affect the entire NetWare server infrastructure. When the FTP service crashes, it may not only terminate file transfer operations but could also potentially impact other services running on the same NetWare server. The abend condition typically requires manual intervention to restart the FTP service and may necessitate system rebooting in severe cases. This type of denial of service attack directly violates the availability principle of the CIA triad and can be exploited by malicious users to disrupt business operations, particularly in environments where file sharing and transfer capabilities are critical for daily operations.
This vulnerability aligns with CWE-121, which describes buffer overflow conditions, and CWE-248, which covers exposure of an exception to external entities. The issue also relates to ATT&CK technique T1499.004, which involves network denial of service attacks through the manipulation of service availability. The root cause stems from inadequate input validation and state management within the FTP server implementation, specifically failing to properly handle command sequences that result in invalid state transitions. Organizations running affected NetWare systems should prioritize applying the vendor-supplied patches that address this specific command sequence handling issue. The mitigation approach should include implementing proper access controls to limit FTP service exposure and monitoring for unusual command patterns that might indicate exploitation attempts. Additionally, network segmentation and firewall rules can help reduce the attack surface by limiting access to the FTP service to only trusted network segments.