CVE-2009-4108 in XM Easy Personal FTP Server
Summary
by MITRE
XM Easy Personal FTP Server 5.8.0 allows remote authenticated users to cause a denial of service (crash) by uploading or creating a large number of files or directories, then performing a LIST command.
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Analysis
by VulDB Data Team • 10/14/2025
The vulnerability identified as CVE-2009-4108 affects XM Easy Personal FTP Server version 5.8.0 and represents a denial of service condition that can be exploited by authenticated remote attackers. This flaw manifests when an attacker uploads or creates an excessive number of files or directories within the server environment, subsequently executing a LIST command that triggers the server crash. The vulnerability operates through a resource exhaustion mechanism where the server fails to properly handle the large volume of directory entries during the listing operation, leading to a complete service interruption.
The technical implementation of this vulnerability stems from inadequate input validation and resource management within the FTP server's directory listing functionality. When the LIST command is executed against a directory containing a massive number of files or subdirectories, the server's memory management and processing capabilities become overwhelmed. This represents a classic case of insufficient bounds checking and memory allocation handling that aligns with CWE-129, which addresses issues related to insufficient checking of the length, size, or count of data. The flaw specifically impacts the server's ability to process directory listings efficiently, causing memory exhaustion or stack overflow conditions that result in the application crashing and becoming unavailable to legitimate users.
The operational impact of this vulnerability extends beyond simple service disruption as it can severely compromise the availability of critical file transfer services. Organizations relying on XM Easy Personal FTP Server for their file management operations face significant risks when this vulnerability is exploited, as the denial of service can prevent legitimate users from accessing or transferring files. The attack requires only authenticated access, making it particularly dangerous as it can be executed by malicious insiders or compromised accounts. This vulnerability also demonstrates poor defensive programming practices that align with ATT&CK technique T1499.1, which covers the use of network denial of service attacks to disrupt services. The impact is particularly severe in environments where FTP services are critical for business operations, as the server crash can result in extended downtime and potential data access restrictions.
Mitigation strategies for CVE-2009-4108 should focus on implementing proper resource management and input validation within the FTP server software. System administrators should consider applying available patches or updates from the vendor to address the underlying memory management issues. Additionally, implementing rate limiting and resource quotas for file operations can help prevent attackers from creating excessive directory structures that could lead to service disruption. Network-level monitoring should be enhanced to detect unusual patterns of file creation followed by LIST commands that could indicate exploitation attempts. The implementation of proper error handling and memory allocation routines within the FTP server's directory listing functionality would prevent the crash condition from occurring. Organizations should also consider implementing intrusion detection systems that can identify and alert on suspicious file creation patterns that may precede denial of service attacks. Regular security assessments and vulnerability scanning should be conducted to identify similar resource exhaustion vulnerabilities in other network services that may be susceptible to analogous attacks.