CVE-2001-0769 in GuildFTPd
Summary
by MITRE
Memory leak in GuildFTPd Server 0.97 allows remote attackers to cause a denial of service via a request containing a null character.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 10/04/2025
The vulnerability identified as CVE-2001-0769 represents a critical memory leak flaw within the GuildFTPd Server version 0.97 that fundamentally compromises system stability and availability. This memory leak occurs when the server processes incoming requests containing null characters, creating a condition where allocated memory resources are not properly released back to the system. The flaw specifically targets the FTP server's handling of malformed input data, where a remote attacker can exploit this weakness by sending carefully crafted requests that include null terminators. The vulnerability stems from inadequate input validation and memory management practices within the server's protocol handling mechanisms.
The technical implementation of this vulnerability manifests through the server's failure to properly manage memory allocation during request processing. When a null character is encountered within an FTP command or data transfer, the GuildFTPd Server does not correctly handle the termination sequence, leading to progressive memory consumption without proper deallocation. This memory exhaustion eventually results in the server becoming unresponsive or crashing entirely, thereby enabling a denial of service condition that affects legitimate users attempting to access the FTP services. The flaw operates at the application layer of the network stack, specifically within the FTP protocol implementation where input parsing and memory management intersect. This issue aligns with CWE-401, which describes improper handling of memory allocation failures, and represents a classic example of resource leak vulnerabilities that can be exploited for denial of service attacks.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise the entire FTP infrastructure. Remote attackers can systematically consume available memory resources through repeated exploitation attempts, leading to complete service unavailability for legitimate users. The vulnerability affects any system running GuildFTPd Server 0.97, making it particularly dangerous in environments where FTP services are critical for business operations. The attack vector requires minimal technical expertise, as it only necessitates sending malformed requests containing null characters, making it accessible to attackers with basic network knowledge. This vulnerability directly maps to ATT&CK technique T1499.004, which covers network denial of service attacks, and represents a common pattern where resource exhaustion leads to service disruption. Organizations may experience cascading effects where the FTP service failure impacts related systems that depend on file transfer capabilities, potentially leading to broader operational disruptions.
Mitigation strategies for CVE-2001-0769 should prioritize immediate patching of the GuildFTPd Server to the latest available version that addresses the memory leak issue. System administrators should implement network-level filtering to block requests containing null characters, though this approach may impact legitimate traffic if not carefully configured. The implementation of monitoring systems to detect unusual memory consumption patterns can provide early warning of potential exploitation attempts. Additionally, organizations should consider implementing intrusion detection systems that can identify and block malformed FTP requests. The vulnerability highlights the importance of proper input validation and memory management practices in server software development, as outlined in secure coding guidelines such as those provided by the Open Web Application Security Project. Regular security assessments and vulnerability scanning should be conducted to identify similar issues in other server applications, particularly those handling network protocols with complex parsing requirements. System hardening measures including limiting FTP service access to trusted networks and implementing proper access controls can further reduce the attack surface while patches are being deployed.