CVE-2006-0705 in SSH Server
Summary
by MITRE
Format string vulnerability in a logging function as used by various SFTP servers, including (1) AttachmateWRQ Reflection for Secure IT UNIX Server before 6.0.0.9, (2) Reflection for Secure IT Windows Server before 6.0 build 38, (3) F-Secure SSH Server for Windows before 5.3 build 35, (4) F-Secure SSH Server for UNIX 3.0 through 5.0.8, (5) SSH Tectia Server 4.3.6 and earlier and 4.4.0, and (6) SSH Shell Server 3.2.9 and earlier, allows remote authenticated users to execute arbitrary commands via unspecified vectors, involving crafted filenames and the stat command.
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Analysis
by VulDB Data Team • 06/22/2025
This vulnerability represents a critical format string flaw in logging functions of multiple SFTP server implementations that enables remote authenticated attackers to execute arbitrary code. The vulnerability exists within the way these servers handle filename logging operations, specifically when processing filenames through the stat command. The flaw allows attackers to craft malicious filenames that contain format specifiers which, when processed by the vulnerable logging function, can lead to arbitrary code execution. This type of vulnerability falls under the CWE-134 category of format string vulnerabilities where untrusted data is used as a format string parameter without proper validation or sanitization. The affected products span multiple vendors including Attachmate, F-Secure, and SSH Tectia, indicating a widespread issue affecting core authentication and file transfer server functionality.
The technical exploitation mechanism involves authenticated users leveraging crafted filenames that contain format string specifiers such as %x, %s, or %n which are then processed by the vulnerable logging function. When these specifiers are encountered during log output generation, they can cause the logging function to read from or write to arbitrary memory locations, potentially leading to stack corruption, information disclosure, or code execution. The vulnerability is particularly dangerous because it operates at the logging level where it can be triggered by normal file operations, and the attack vectors involve common commands like stat that are frequently used in SFTP operations. This aligns with ATT&CK technique T1059.007 for command and script injection, where attackers can manipulate logging functions to execute arbitrary commands within the server context.
The operational impact of this vulnerability extends beyond simple privilege escalation to full system compromise, as authenticated users can leverage this flaw to gain unauthorized access to server resources. The vulnerability affects servers that are typically critical infrastructure components, making the potential damage significant for organizations relying on secure file transfer protocols. Attackers can potentially extract sensitive information from memory, overwrite critical function pointers, or inject malicious code that persists across server restarts. The widespread nature of affected products means that organizations using multiple SSH/SFTP implementations across their infrastructure face elevated risk. Security practitioners should note that this vulnerability is particularly concerning because it requires minimal privileges to exploit and can be triggered through normal file system operations, making detection and prevention challenging.
Mitigation strategies for this vulnerability include immediate patching of all affected server implementations to address the format string handling in logging functions. Organizations should implement network segmentation to limit access to SFTP servers and reduce the attack surface for authenticated users. Input validation and sanitization measures should be strengthened at all points where user-supplied filenames are processed, particularly in logging contexts. Monitoring for unusual logging patterns or attempts to exploit format string vulnerabilities should be implemented through security information and event management systems. Additionally, implementing principle of least privilege access controls and regular security audits of authentication and file transfer configurations can help reduce the impact if exploitation occurs. The vulnerability demonstrates the importance of proper input validation and secure coding practices in server-side applications, particularly in logging and error handling functions that process user-supplied data.