CVE-2005-2238 in AIX
Summary
by MITRE
ftpd in IBM AIX 5.1, 5.2 and 5.3 allows remote authenticated users to cause a denial of service (port exhaustion and memory consumption) by using all ephemeral ports.
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Analysis
by VulDB Data Team • 06/30/2025
The vulnerability described in CVE-2005-2238 affects the ftpd service running on IBM AIX operating systems version 5.1, 5.2, and 5.3. This represents a significant security flaw that enables remote authenticated users to perform denial of service attacks against the system. The issue stems from how the ftpd service manages network connections and port allocation during file transfer operations. The vulnerability is particularly concerning because it can be exploited by attackers who have already gained authentication credentials, making it a serious concern for systems where access controls may be compromised or where insider threats exist.
The technical flaw lies in the improper handling of ephemeral port allocation within the ftpd service implementation. When authenticated users establish FTP connections, the service creates multiple socket connections that consume ephemeral ports from the system's available port pool. The vulnerability occurs because the service does not properly manage or limit the number of concurrent connections that can be established, leading to exhaustion of the ephemeral port range. This port exhaustion causes the system to become unable to establish new network connections, effectively creating a denial of service condition. The memory consumption aspect of this vulnerability occurs as the system accumulates connection state information for each failed connection attempt, gradually depleting available memory resources.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise system stability and availability. When ephemeral ports are exhausted, legitimate network services may be unable to establish new connections, affecting not just FTP services but potentially other applications that depend on TCP connectivity. The memory consumption aspect can lead to system slowdowns or complete system crashes, depending on the severity of resource exhaustion. This vulnerability particularly affects enterprise environments where AIX systems serve as file servers or where FTP services are heavily utilized. The impact is amplified in environments where multiple users may simultaneously exploit this weakness, creating cascading failures that can affect entire network segments.
Organizations should implement immediate mitigations including applying the relevant IBM AIX security patches that address this specific vulnerability. System administrators should also consider implementing connection rate limiting and monitoring for unusual patterns of FTP connection establishment. The vulnerability aligns with CWE-1104 which describes improper restriction of excessive authentication attempts, and it relates to ATT&CK technique T1499.004 for network denial of service attacks. Additionally, implementing proper network segmentation and access controls can help limit the scope of potential exploitation, ensuring that only authorized users can access the affected FTP services. Regular security audits and monitoring of system resources should be conducted to detect early signs of port exhaustion or memory consumption anomalies that may indicate exploitation attempts.