CVE-2001-1156 in FTP Server
Summary
by MITRE
TYPSoft FTP 0.95 allows remote attackers to cause a denial of service (CPU consumption) via a "../../*" argument to (1) STOR or (2) RETR.
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Analysis
by VulDB Data Team • 09/27/2025
The vulnerability identified as CVE-2001-1156 affects TYPSoft FTP server version 0.95 and represents a significant denial of service weakness that can be exploited by remote attackers to consume excessive system resources. This flaw specifically targets the server's handling of file transfer commands, particularly the STOR and RETR operations, which are fundamental components of the File Transfer Protocol. The vulnerability exploits a path traversal pattern using the "../../*" argument that causes the FTP server to process directory structures in a manner that leads to excessive cpu utilization and system resource exhaustion.
The technical implementation of this vulnerability stems from inadequate input validation and path resolution mechanisms within the TYPSoft FTP server implementation. When an attacker submits a malformed path argument containing the "../../*" pattern to either the STOR or RETR commands, the server fails to properly sanitize or limit the directory traversal operations. This results in the server recursively processing directory structures in a way that consumes disproportionate cpu cycles and memory resources, ultimately leading to system instability and denial of service conditions for legitimate users attempting to access the ftp service.
From an operational impact perspective, this vulnerability presents a critical risk to organizations relying on TYPSoft FTP 0.95 servers for file transfer operations. The denial of service condition can effectively render the ftp service unavailable to legitimate users, potentially disrupting business operations and data transfer workflows. The vulnerability is particularly concerning because it requires minimal effort from attackers to exploit, as the malicious argument can be crafted easily and does not require authentication or specialized tools. The resource consumption pattern typically results in high cpu utilization that may affect not only the ftp service but also other system processes and overall server performance.
This vulnerability aligns with CWE-22 Path Traversal and CWE-400 Uncontrolled Resource Consumption, representing a classic example of how improper input validation can lead to resource exhaustion attacks. The attack vector follows patterns consistent with the ATT&CK framework's T1499 resource exhaustion techniques, where adversaries target system resources to disrupt service availability. Organizations should consider implementing network-level mitigations such as firewall rules to restrict access to ftp ports, deploying intrusion detection systems to monitor for suspicious path traversal patterns, and applying immediate patches or updates to resolve the vulnerability. The recommended solution involves upgrading to a patched version of TYPSoft FTP server or implementing application-level controls that validate and limit directory traversal operations to prevent exploitation of this specific vulnerability pattern.