CVE-2001-0827 in Ceberus FTP Server
Summary
by MITRE
Cerberus FTP server 1.0 - 1.5 allows remote attackers to cause a denial of service (crash) via a large number of "PASV" requests.
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Analysis
by VulDB Data Team • 04/23/2025
The Cerberus FTP server vulnerability CVE-2001-0827 represents a classic denial of service flaw that emerged in versions 1.0 through 1.5 of this ftp server implementation. This vulnerability specifically targets the server's handling of passive mode connection requests, which are fundamental components of the ftp protocol used for data channel establishment. The flaw manifests when remote attackers flood the server with an excessive number of PASV command requests, ultimately leading to a complete service disruption. The vulnerability falls under the category of resource exhaustion attacks where the attacker leverages the server's response handling mechanisms to consume available system resources. This type of attack directly violates the availability principle of the CIA security triad by making the service inaccessible to legitimate users.
The technical implementation of this vulnerability stems from inadequate input validation and resource management within the Cerberus FTP server's passive mode handling logic. When processing multiple PASV requests in rapid succession, the server fails to properly manage its internal state and connection resources, leading to a condition where the server's memory structures become corrupted or exhausted. The server's response to each PASV command typically involves allocating temporary resources and preparing for potential data connections, but when these requests are sent in large volumes, the server's resource management becomes overwhelmed. This behavior aligns with CWE-400, which addresses "Uncontrolled Resource Consumption" and represents a common pattern in legacy server implementations where proper resource limits and request queuing mechanisms were not adequately implemented. The vulnerability demonstrates poor defensive programming practices where the server lacks proper rate limiting or resource exhaustion protection mechanisms.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise the entire ftp service infrastructure. Attackers can exploit this flaw without requiring authentication, making it particularly dangerous as it can be executed from any network location. The DoS condition typically results in the server crashing or becoming unresponsive, requiring manual intervention and system restarts to restore normal operations. Organizations relying on Cerberus FTP servers for file transfer operations face significant operational risks including data transfer delays, service unavailability during critical business hours, and potential loss of productivity. The vulnerability also creates opportunities for attackers to conduct further reconnaissance or launch additional attacks against the compromised system. From an attacker's perspective, this represents a low-effort, high-impact method of service disruption that aligns with ATT&CK technique T1499.004 for "Endpoint Denial of Service" and demonstrates the importance of implementing proper input validation and resource management in network services.
Mitigation strategies for this vulnerability require immediate attention through software updates and configuration changes. The most effective approach involves upgrading to a newer version of the Cerberus FTP server that contains proper resource management and rate limiting mechanisms. Administrators should implement network-level restrictions to limit the number of connections or requests from individual clients, particularly for ftp control commands. The server configuration should include proper timeouts and connection limits to prevent resource exhaustion. Additionally, implementing intrusion detection systems can help identify and block malicious traffic patterns associated with this attack vector. Network segmentation and firewall rules can further limit the exposure of vulnerable ftp services to external threats. The vulnerability also highlights the importance of regular security assessments and patch management procedures, as this flaw existed in multiple versions of the software and could have been addressed through proper software maintenance practices. Organizations should also consider implementing monitoring solutions that can detect unusual patterns of PASV requests and automatically trigger alerts or defensive measures.