CVE-2006-6750 in XM Easy Personal FTP Server
Summary
by MITRE
Format string vulnerability in XM Easy Personal FTP Server 5.0.1 allows remote attackers to cause a denial of service (application crash) via format string specifiers in a long PORT command. NOTE: this issue might be related to CVE-2006-2226.
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Analysis
by VulDB Data Team • 09/29/2017
The vulnerability identified as CVE-2006-6750 represents a format string vulnerability within XM Easy Personal FTP Server version 5.0.1 that exposes the system to remote denial of service attacks. This flaw occurs when the server processes a specially crafted PORT command containing format string specifiers that exceed normal parameter expectations. The vulnerability specifically manifests in the server's handling of user input during FTP protocol operations, where improper validation and processing of the PORT command allows malicious actors to inject format specifiers that can trigger application instability.
This type of vulnerability falls under the CWE-134 category of "Use of Externally-Controlled Format String" which is classified as a critical security weakness in software systems. The flaw operates at the application layer where the FTP server fails to properly sanitize user-supplied input before using it in format string functions. When a long PORT command is received with maliciously crafted format specifiers, the server's internal string processing functions interpret these specifiers as instructions rather than plain text data, leading to unpredictable behavior and potential memory corruption.
The operational impact of this vulnerability extends beyond simple service disruption to potentially expose the underlying system to more sophisticated attacks. Remote attackers can leverage this weakness to cause application crashes that result in complete denial of service for legitimate users attempting to access the FTP server. The vulnerability affects the availability aspect of the CIA security triad by preventing authorized users from accessing the file transfer services. Additionally, the crash conditions may provide opportunities for attackers to gain insights into memory layout or potentially escalate the attack vector through memory corruption exploitation techniques.
The attack surface for this vulnerability is primarily limited to the FTP protocol interface where the PORT command is processed, but its impact can be significant for organizations relying on this server for file transfer operations. The vulnerability's relationship to CVE-2006-2226 suggests a broader pattern of similar format string issues within the same software product or related implementations, indicating potential systemic weaknesses in input validation practices. Security professionals should note that this vulnerability aligns with ATT&CK technique T1210 - "Exploitation of Remote Services" and T1499 - "Endpoint Denial of Service" in the MITRE ATT&CK framework, as it enables remote attackers to disrupt service availability through application-level exploitation.
Mitigation strategies for this vulnerability should include immediate patching of the XM Easy Personal FTP Server to a version that properly validates and sanitizes format string inputs. Organizations should implement network segmentation to limit exposure of FTP services to trusted networks only, and deploy intrusion detection systems to monitor for suspicious PORT command patterns. Input validation should be strengthened at the application level to ensure that all user-supplied data is properly escaped or sanitized before being processed in any format string operations. System administrators should also consider implementing rate limiting and connection monitoring to detect and prevent abuse of the vulnerable FTP command interface. The vulnerability serves as a reminder of the critical importance of proper input validation and the dangers of using user-controlled data in format string functions without adequate sanitization measures.