CVE-2000-0573 in wu-ftpd
Summary
by MITRE
The lreply function in wu-ftpd 2.6.0 and earlier does not properly cleanse an untrusted format string, which allows remote attackers to execute arbitrary commands via the SITE EXEC command.
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Analysis
by VulDB Data Team • 12/20/2024
The vulnerability described in CVE-2000-0573 represents a critical format string vulnerability within the wu-ftpd FTP server implementation. This flaw exists specifically within the lreply function of wu-ftpd versions 2.6.0 and earlier, where the software fails to properly sanitize user-supplied input before incorporating it into format string operations. The vulnerability manifests when attackers exploit the SITE EXEC command, which is designed to execute system commands on the FTP server. The improper handling of format strings creates a pathway for remote code execution, allowing malicious actors to gain unauthorized access to the underlying system.
The technical exploitation of this vulnerability stems from the function's failure to validate or escape format specifiers present in user-provided data. When the lreply function processes input through the SITE EXEC command, it directly incorporates untrusted data into printf-style format string operations without proper sanitization. This creates a classic format string vulnerability that can be leveraged to manipulate memory contents, execute arbitrary code, or even cause denial of service conditions. The vulnerability falls under the Common Weakness Enumeration category of CWE-134, which specifically addresses the use of format strings with user-supplied data. The attack vector requires no authentication, making it particularly dangerous as it allows remote exploitation from any network location.
From an operational impact perspective, this vulnerability provides attackers with complete system compromise capabilities, as the SITE EXEC command essentially allows arbitrary command execution with the privileges of the FTP daemon process. The implications extend beyond simple unauthorized access to include potential data exfiltration, system reconnaissance, and establishment of persistent backdoors. The vulnerability's severity is amplified by the widespread use of wu-ftpd in the early 2000s, making numerous systems susceptible to exploitation. This type of vulnerability aligns with ATT&CK technique T1059.001 for command and script interpreter, where adversaries leverage system command execution capabilities to achieve their objectives. The lack of input validation creates a direct pathway for attackers to manipulate the program's execution flow and inject malicious payloads.
The recommended mitigations for this vulnerability include immediate patching of wu-ftpd installations to versions that properly sanitize format string inputs and implement proper input validation. System administrators should also consider implementing network segmentation and access controls to limit exposure of FTP services to untrusted networks. Additional defensive measures include monitoring for suspicious SITE EXEC command usage, implementing intrusion detection systems to detect exploitation attempts, and conducting regular vulnerability assessments of network services. The vulnerability demonstrates the critical importance of proper input validation and the dangers of format string handling in network services. Organizations should also consider migrating to more modern FTP implementations that have addressed these historical security issues and provide better protection against similar classes of vulnerabilities. The incident underscores the necessity of following secure coding practices and adhering to security standards that prevent format string vulnerabilities through proper input sanitization and output formatting techniques.