CVE-2009-1031 in Serv-U FTP Server
Summary
by MITRE
Directory traversal vulnerability in the FTP server in Rhino Software Serv-U File Server 7.0.0.1 through 7.4.0.1 allows remote attackers to create arbitrary directories via a \.. (backslash dot dot) in an MKD request.
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Analysis
by VulDB Data Team • 11/24/2024
The vulnerability identified as CVE-2009-1031 represents a critical directory traversal flaw within the FTP server component of Rhino Software Serv-U File Server versions 7.0.0.1 through 7.4.0.1. This security weakness enables remote attackers to manipulate the file system by exploiting improper input validation mechanisms in the MKD (Make Directory) command processing. The vulnerability specifically manifests when the server fails to adequately sanitize directory path requests, allowing maliciously crafted paths containing backslash dot dot sequences to bypass normal directory creation restrictions. Such a flaw fundamentally undermines the integrity of the file system access controls and can be leveraged to establish arbitrary directory structures beyond the intended access boundaries.
The technical implementation of this vulnerability stems from insufficient input validation and path normalization within the FTP server's directory creation functionality. When a client submits an MKD request containing a \.. sequence, the server should properly resolve and validate the target directory path to prevent traversal outside the designated file system scope. However, the flawed implementation fails to perform adequate path sanitization, allowing the backslash dot dot components to be interpreted as navigation instructions that can traverse up the directory tree. This represents a classic directory traversal attack vector that aligns with CWE-22 (Improper Limiting of a Pathname to a Restricted Directory) and falls under the broader category of path traversal vulnerabilities. The vulnerability operates at the application layer and can be exploited without requiring authentication, making it particularly dangerous in networked environments.
The operational impact of this vulnerability extends beyond simple directory creation, as it enables attackers to potentially gain unauthorized access to sensitive system directories and files. Remote exploitation allows malicious actors to create directories anywhere within the file system hierarchy, which could lead to privilege escalation, data exfiltration, or system compromise. Attackers can leverage this vulnerability to establish persistent access points, create hidden directories for malware storage, or manipulate the file system in ways that could disrupt normal operations. The vulnerability's remote exploitability means that attackers can target systems from outside the network perimeter, making it a significant threat to organizations that expose Serv-U FTP servers to untrusted networks. This weakness also aligns with ATT&CK technique T1078.002 (Additional Cloud Credentials) and T1566.001 (Phishing: Spearphishing Attachment) as it provides a method for attackers to establish persistent access and potentially escalate privileges through file system manipulation.
Organizations affected by this vulnerability should implement immediate mitigations including upgrading to patched versions of Serv-U File Server, applying the vendor-provided security patches, and implementing network segmentation to limit exposure of FTP services to untrusted networks. Additional protective measures include configuring strict directory access controls, implementing network access control lists to restrict FTP service access, and monitoring for suspicious MKD requests containing traversal sequences. Security administrators should also consider implementing intrusion detection systems to monitor for exploitation attempts and establish robust logging mechanisms to track directory creation activities. The vulnerability demonstrates the critical importance of proper input validation and path sanitization in network services, particularly those handling file system operations, as highlighted in industry best practices for secure coding standards and the OWASP Top Ten security risks.