CVE-2009-0967 in Serv-U FTP Server
Summary
by MITRE
The FTP server in Serv-U 7.0.0.1 through 7.4.0.1 allows remote authenticated users to cause a denial of service (service hang) via a large number of SMNT commands without an argument.
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Analysis
by VulDB Data Team • 11/24/2024
The vulnerability identified as CVE-2009-0967 affects the FTP server component within Serv-U versions 7.0.0.1 through 7.4.0.1, representing a significant denial of service weakness that can be exploited by authenticated remote attackers. This issue stems from inadequate input validation within the server's handling of SMNT commands, which are typically used to mount file systems or specify storage locations within FTP operations. The vulnerability is categorized under CWE-20, which describes improper input validation, and aligns with ATT&CK technique T1499.004 for network denial of service attacks.
The technical flaw manifests when an authenticated user sends a large volume of SMNT commands without providing the required argument parameters. This specific command structure bypasses normal validation checks and causes the FTP service to enter a state of continuous processing or hanging, effectively rendering the service unavailable to legitimate users. The vulnerability does not require special privileges beyond authentication, making it particularly dangerous as it can be exploited by any user who has established a connection to the FTP server. The service hang occurs because the server fails to properly handle the malformed command sequence, leading to resource exhaustion or thread blocking within the application's processing logic.
The operational impact of this vulnerability extends beyond simple service disruption, as it can affect business continuity and availability of critical file transfer services. Organizations relying on Serv-U for file sharing and management may experience extended downtime during exploitation, potentially affecting hundreds or thousands of users depending on the scale of the deployment. The vulnerability affects systems where Serv-U serves as the primary FTP server implementation, particularly in enterprise environments where file transfer protocols are heavily utilized for data exchange between departments, partners, or customers. Attackers can leverage this weakness to create sustained service unavailability, making it a preferred method for disrupting business operations without requiring complex attack vectors.
Mitigation strategies for CVE-2009-0967 primarily involve immediate patching of the affected Serv-U versions, as vendors released updates specifically addressing this command handling flaw. Organizations should implement network monitoring to detect unusual patterns of SMNT command usage and establish rate limiting mechanisms to prevent flooding attacks. The implementation of proper input validation and command argument checking within the FTP server configuration can also provide additional defense layers. Security teams should also consider implementing access controls that limit the number of concurrent connections or command processing to minimize the impact of potential exploitation attempts. Additionally, regular security assessments and vulnerability scanning should be conducted to identify similar weaknesses in other FTP server implementations and ensure comprehensive protection against related attack vectors.