CVE-2004-0069 in Windows FTP Server
Summary
by MITRE
Format string vulnerability in HD Soft Windows FTP Server 1.6 and earlier allows remote attackers to execute arbitrary code via format string specifiers in the username, which is processed by the wscanf function.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 09/07/2025
The vulnerability identified as CVE-2004-0069 represents a critical format string flaw in HD Soft Windows FTP Server version 1.6 and earlier implementations. This security weakness stems from improper input validation within the authentication handling mechanism where user-provided credentials are processed through the wscanf function without adequate sanitization. The flaw specifically manifests when the server encounters format string specifiers within the username parameter during the login process, creating an exploitable condition that can be leveraged by remote attackers to gain unauthorized system access.
The technical exploitation of this vulnerability occurs through the manipulation of input data during the authentication phase of the FTP protocol. When the wscanf function processes user input containing format specifiers such as %x, %s, or %n, it interprets these directives as instructions for reading or writing memory locations rather than literal characters. This misinterpretation allows attackers to craft malicious username inputs that can overwrite critical memory addresses, execute arbitrary code, or even cause application crashes. The vulnerability directly maps to CWE-134 which classifies format string vulnerabilities as weaknesses where format strings are constructed from user-controlled data without proper validation or sanitization.
From an operational perspective, this vulnerability presents a severe risk to systems running affected FTP server versions as it enables remote code execution without requiring prior authentication. Attackers can exploit this flaw from any network location to potentially gain full system control, making it particularly dangerous in enterprise environments where FTP services are commonly deployed. The impact extends beyond simple unauthorized access as the vulnerability can be used to establish persistent backdoors, escalate privileges, or deploy additional malware. This weakness significantly undermines the confidentiality, integrity, and availability of the affected systems, particularly when the FTP server is used for sensitive data transfers or serves as a gateway to internal networks.
Security professionals should implement immediate mitigations including applying vendor patches or upgrading to non-vulnerable versions of the HD Soft Windows FTP Server software. Network segmentation and firewall rules can help limit exposure by restricting access to FTP services from untrusted networks. Additionally, monitoring for suspicious authentication attempts containing unusual format string characters should be implemented as part of intrusion detection measures. The vulnerability aligns with ATT&CK technique T1190 which describes the exploitation of vulnerabilities in remote services, and T1059 which covers the execution of malicious code through command injection techniques. Organizations should also consider implementing input validation controls and employing secure coding practices that prevent format string vulnerabilities in custom applications, particularly when dealing with user-supplied data that may be processed through functions like wscanf or similar format string handling routines.