CVE-1999-0880 in wu-ftpd
Summary
by MITRE
Denial of service in WU-FTPD via the SITE NEWER command, which does not free memory properly.
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Analysis
by VulDB Data Team • 10/22/2025
The vulnerability identified as CVE-1999-0880 represents a classic memory management flaw within the WU-FTPD (Washington University FTP Daemon) implementation that enables a denial of service attack through improper memory handling during processing of the SITE NEWER command. This vulnerability specifically affects the WU-FTPD server software version 2.4.2 and earlier versions, where the application fails to properly release allocated memory resources when handling certain FTP commands, creating a condition that can be exploited to exhaust system resources and render the service unavailable to legitimate users.
The technical root cause of this vulnerability lies in the improper memory deallocation mechanism within the SITE NEWER command handler. When an attacker sends a specially crafted SITE NEWER command to the vulnerable FTP server, the application allocates memory to process the request but subsequently fails to properly free this memory before returning control to the main execution flow. This memory leak occurs repeatedly with each command execution, causing the server process to consume increasing amounts of memory over time until system resources are exhausted and the service becomes unresponsive to legitimate FTP connections. The flaw demonstrates characteristics consistent with CWE-401: Improper Release of Memory and falls under the broader category of memory corruption vulnerabilities that have been extensively documented in the cybersecurity community.
The operational impact of this vulnerability extends beyond simple service disruption as it provides attackers with a straightforward method to compromise the availability of FTP services without requiring authentication or advanced exploitation techniques. The vulnerability is particularly concerning because it can be triggered by any remote user with access to the FTP server, making it an attractive target for malicious actors seeking to perform denial of service attacks against network infrastructure. In environments where FTP services are critical for business operations, this vulnerability could result in significant downtime and potential financial losses. The attack vector is simple and reliable, requiring only the transmission of a malformed SITE NEWER command to the target server, which aligns with ATT&CK technique T1499.004: Endpoint Denial of Service, specifically targeting service availability through resource exhaustion.
Mitigation strategies for this vulnerability require immediate attention through software updates and patches provided by the vendor, as the WU-FTPD project has released fixes for this specific memory management issue in subsequent versions. System administrators should prioritize patching affected servers and implementing network-level controls to monitor and restrict FTP command traffic, particularly focusing on limiting access to potentially dangerous commands such as SITE NEWER. Additionally, deploying intrusion detection systems that can identify and alert on anomalous FTP command sequences may help detect exploitation attempts. The vulnerability also underscores the importance of proper memory management practices in server applications and serves as a reminder of the critical need for thorough code review and security testing of network services, particularly those handling user input. Organizations should consider implementing redundant FTP services and failover mechanisms to maintain availability during patch deployment periods, while also establishing monitoring protocols to detect unusual memory consumption patterns that may indicate exploitation attempts.