CVE-2005-3887 in Instant Messenger
Summary
by MITRE
Gadu-Gadu 7.20 does not properly handle MS-DOS device names in filenames, which allows remote attackers to (1) cause a denial of service (hang) via an image filename of AUX: sent twice (hang), or (2) write to the LPT1 port via a filename of "LPT1:".
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Analysis
by VulDB Data Team • 06/24/2018
The vulnerability identified as CVE-2005-3887 affects the Gadu-Gadu instant messaging client version 7.20 and represents a classic operating system-level input validation flaw that exploits legacy MS-DOS device name handling mechanisms. This vulnerability resides in the file name processing subsystem of the application, where it fails to properly sanitize or reject filenames that contain MS-DOS device names such as AUX, LPT1, CON, PRN, and others. These device names were originally designed for Windows 3.x and earlier versions to provide access to hardware devices and system resources, but they continue to function in modern Windows environments as special device handles that can be accessed through the file system interface.
The technical exploitation of this vulnerability occurs through two distinct attack vectors that leverage the Windows operating system's handling of device names in file paths. In the first scenario, an attacker can send an image file with the filename "AUX:" to a victim using the Gadu-Gadu client, and when the application attempts to process this filename, it causes a denial of service condition that results in the application hanging or freezing. This happens because the application's file processing logic does not properly handle the special device name "AUX:" which is interpreted by the Windows kernel as a reference to the auxiliary device, causing the application to enter an infinite loop or resource contention state. The second attack vector involves sending a file with the name "LPT1:" which allows an attacker to write data directly to the parallel port LPT1, effectively bypassing normal file system access controls and potentially enabling arbitrary code execution or system-level manipulation.
This vulnerability directly maps to CWE-174, which describes the weakness of "Double-encoding in a resource name," and also relates to CWE-77 and CWE-78, which address command injection and improper input sanitization issues. The operational impact of this vulnerability extends beyond simple denial of service to potentially enable more serious system compromise. The ability to write to LPT1 port represents a particularly concerning aspect as it could allow attackers to send malicious data to attached hardware devices such as printers, potentially causing damage to hardware or enabling side-channel attacks. From an attacker's perspective, this vulnerability aligns with ATT&CK technique T1059.007 for command and scripting interpreter, and T1068 for exploit for privilege escalation, as it provides a means to manipulate system resources through file system interactions. The vulnerability demonstrates a fundamental flaw in input validation practices, where the application fails to implement proper sanitization of user-provided filenames before processing them through the operating system's file handling mechanisms.
The mitigation strategies for this vulnerability should focus on implementing comprehensive input validation and sanitization at multiple layers of the application architecture. First, the application should reject any filenames containing MS-DOS device names through a whitelist approach that explicitly defines valid characters and patterns for file names. Second, the application should implement proper error handling and timeout mechanisms to prevent hanging conditions when processing potentially malicious filenames. Third, the application should avoid direct interaction with the file system for user-provided filenames without proper validation, instead using a sandboxed or sanitized file processing pipeline. Additionally, system administrators should consider implementing network-level filtering to prevent the transmission of files with suspicious naming patterns, and application developers should conduct regular security code reviews focusing on input validation and resource handling. The vulnerability highlights the importance of understanding legacy operating system behaviors and their potential impact on modern applications, particularly those handling user-generated content or file transfers through network protocols.