CVE-2011-1137 in ProFTPD
Summary
by MITRE
Integer overflow in the mod_sftp (aka SFTP) module in ProFTPD 1.3.3d and earlier allows remote attackers to cause a denial of service (memory consumption leading to OOM kill) via a malformed SSH message.
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Analysis
by VulDB Data Team • 08/25/2024
The vulnerability identified as CVE-2011-1137 represents a critical integer overflow flaw within the mod_sftp module of ProFTPD versions 1.3.3d and earlier. This vulnerability specifically affects the Secure File Transfer Protocol implementation within the ProFTPD server software, creating a pathway for remote attackers to exploit memory handling inconsistencies. The flaw manifests when the system processes malformed SSH messages, leading to improper integer arithmetic that can result in excessive memory allocation and consumption.
The technical root cause of this vulnerability lies in the improper handling of integer values during the processing of SSH protocol messages within the SFTP module. When an attacker sends a specially crafted SSH message containing malformed data, the integer overflow condition occurs during the calculation of memory allocation requirements. This overflow results in the system attempting to allocate an unexpectedly large amount of memory, which can quickly exhaust available system resources and trigger the operating system's Out-of-Memory (OOM) killer mechanism. The vulnerability falls under the CWE-190 category of Integer Overflow or Wraparound, which is a well-documented weakness in software systems where integer arithmetic produces results that exceed the maximum value representable by the data type.
From an operational perspective, this vulnerability presents a significant denial of service risk to systems running vulnerable ProFTPD versions. The impact extends beyond simple service disruption as the memory consumption pattern can overwhelm system resources and potentially affect other running processes on the same host. Attackers can exploit this vulnerability remotely without requiring authentication credentials, making it particularly dangerous in publicly accessible server environments. The OOM kill mechanism typically results in the forced termination of the ProFTPD process, effectively rendering the file transfer service unavailable to legitimate users while potentially causing cascading effects on system stability and performance.
The exploitation of this vulnerability aligns with ATT&CK technique T1499.004, which involves network denial of service attacks targeting system resources. Organizations running affected ProFTPD versions face a critical security risk that requires immediate attention. The vulnerability demonstrates the importance of proper input validation and integer arithmetic handling in network protocol implementations. Security practitioners should note that this issue affects not only the immediate availability of the FTP service but also represents a broader class of memory corruption vulnerabilities that can lead to system instability and potential privilege escalation in more complex attack scenarios.
Mitigation strategies for CVE-2011-1137 include immediate deployment of updated ProFTPD versions that contain patches addressing the integer overflow condition in the mod_sftp module. System administrators should also implement network-level protections such as firewall rules that limit access to SFTP ports and monitor for unusual memory consumption patterns. Additionally, configuring resource limits and process monitoring can help detect and mitigate the impact of successful exploitation attempts. The vulnerability underscores the importance of maintaining current software versions and conducting regular security assessments of network services to identify and remediate similar integer overflow conditions that could affect other components of the system infrastructure.