CVE-2011-4130 in ProFTPD
Summary
by MITRE
Use-after-free vulnerability in the Response API in ProFTPD before 1.3.3g allows remote authenticated users to execute arbitrary code via vectors involving an error that occurs after an FTP data transfer.
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Analysis
by VulDB Data Team • 11/27/2021
The CVE-2011-4130 vulnerability represents a critical use-after-free flaw in the ProFTPD Response API that affects versions prior to 1.3.3g. This vulnerability arises from improper memory management practices within the FTP server's response handling mechanism, specifically during error conditions that occur after FTP data transfers have been completed. The flaw exists in the way ProFTPD manages memory allocation and deallocation for response objects, creating a scenario where freed memory can be accessed and potentially overwritten by subsequent operations.
The technical exploitation of this vulnerability occurs when an authenticated remote user initiates an FTP data transfer and subsequently triggers an error condition within the Response API. During this process, the FTP server allocates memory for response objects but fails to properly invalidate pointers after freeing the associated memory blocks. When the error condition is processed, the system attempts to access previously freed memory locations, leading to a use-after-free condition that can be leveraged by attackers to execute arbitrary code with the privileges of the ProFTPD process. This memory corruption vulnerability is particularly dangerous because it allows remote authenticated attackers to gain system-level access without requiring additional privileges.
From an operational impact perspective, this vulnerability compromises the integrity and availability of FTP services by enabling remote code execution capabilities. Attackers can exploit this flaw to gain unauthorized access to the server, potentially leading to complete system compromise, data exfiltration, or establishment of persistent backdoors. The vulnerability affects organizations relying on ProFTPD for file transfer services, particularly those with less restrictive access controls or inadequate monitoring of authenticated user activities. The remote nature of the attack means that exploitation can occur from anywhere on the network, making it particularly concerning for organizations with public FTP servers or those exposed to the internet.
The vulnerability aligns with CWE-416, which specifically addresses the use of freed memory condition in software systems, and demonstrates characteristics consistent with the attack patterns documented in the MITRE ATT&CK framework under the T1059 technique for command and control through remote access tools. Organizations should implement immediate mitigations including upgrading to ProFTPD version 1.3.3g or later, which contains the necessary memory management fixes. Additional defensive measures include implementing network segmentation to limit access to FTP services, enabling robust monitoring of FTP data transfer activities, and deploying intrusion detection systems to detect anomalous FTP behavior patterns. System administrators should also consider disabling unnecessary FTP features and implementing strict access controls to minimize the attack surface. Regular security assessments and vulnerability scanning should be conducted to identify any potential exploitation attempts, while maintaining up-to-date threat intelligence to track emerging attack patterns targeting FTP services.