CVE-2011-0507 in BlackMoon FTP Server
Summary
by MITRE
FTPService.exe in Blackmoon FTP 3.1 Build 1735 and Build 1736 (3.1.7.1736), and possibly other versions before 3.1.8.1737, allows remote attackers to cause a denial of service (crash) via a large number of PORT commands with long arguments, which triggers a NULL pointer dereference. NOTE: some of these details are obtained from third party information.
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Analysis
by VulDB Data Team • 01/19/2025
The vulnerability described in CVE-2011-0507 represents a critical denial of service flaw within the Blackmoon FTP server software, specifically affecting versions 3.1 Build 1735 and 1736. This issue manifests through the FTPService.exe component which fails to properly validate input parameters when processing PORT commands from remote clients. The flaw occurs when attackers submit a large volume of PORT commands containing excessively long arguments, leading to a system crash due to improper memory management. The vulnerability stems from a NULL pointer dereference condition that occurs during command processing, where the software attempts to access memory locations that have not been properly initialized or allocated.
From a technical perspective, this vulnerability operates at the application layer of the network stack and directly impacts the FTP service's ability to maintain stable operations. The flaw is classified under CWE-476 which specifically addresses NULL pointer dereference conditions in software applications. When the FTP service receives malformed PORT commands with extended argument lengths, the internal parsing mechanism fails to handle these inputs gracefully, resulting in a segmentation fault or access violation that terminates the service process. The attack vector requires only network connectivity to the affected FTP server and does not necessitate authentication or elevated privileges, making it particularly dangerous for publicly accessible FTP services.
The operational impact of this vulnerability extends beyond simple service disruption, as it can be exploited to repeatedly crash the FTP service and potentially render the entire file transfer capability unusable for legitimate users. Attackers can leverage this flaw to perform sustained denial of service attacks against FTP servers running affected versions, causing significant business disruption and potentially affecting other services that depend on file transfer capabilities. The vulnerability affects not just the specific builds mentioned but likely extends to other versions prior to 3.1.8.1737, creating a broad attack surface for malicious actors. This type of vulnerability aligns with ATT&CK technique T1499.004 which covers network denial of service attacks and represents a classic example of how improper input validation can lead to service availability compromise.
Mitigation strategies for this vulnerability primarily involve immediate patching of the affected software to version 3.1.8.1737 or later, which contains the necessary code fixes to properly handle malformed PORT commands. Network administrators should implement rate limiting mechanisms to restrict the number of PORT commands that can be processed within a given time period, effectively preventing abuse of this particular vulnerability. Additionally, deploying intrusion detection systems that can identify and block suspicious FTP traffic patterns may provide an additional layer of protection. Organizations should also consider implementing network segmentation to limit exposure of FTP services to untrusted networks and ensure that only necessary ports are accessible from external networks. The vulnerability demonstrates the importance of robust input validation and proper error handling in network services, as highlighted by industry best practices in secure coding standards and the principles outlined in the OWASP Top Ten security risks.