CVE-2004-2530 in Instant Messenger
Summary
by MITRE
Visual truncation vulnerability in Gadu-Gadu allows remote attackers to spoof the file extension on transmitted files via a filename with a large number of spaces followed by the real extension, which is not displayed in the dialog box.
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Analysis
by VulDB Data Team • 09/04/2025
The visual truncation vulnerability in Gadu-Gadu represents a classic case of user interface manipulation that exploits how applications handle filename display and validation. This vulnerability specifically affects the Gadu-Gadu instant messaging client which was widely used in eastern european markets and operated on the principle of displaying file transfer information within dialog boxes that had limited display capacity. The flaw manifests when a malicious actor crafts a filename containing an excessive number of spaces followed by a legitimate file extension, creating a deceptive visual representation that obscures the actual file type.
The technical implementation of this vulnerability relies on the client's insufficient input validation and display handling mechanisms. When a user receives a file transfer request, the Gadu-Gadu client processes the filename through a display routine that truncates or clips the filename to fit within the dialog box constraints. The attacker can exploit this by creating a filename such as "document.txt" where the actual filename is "document....................txt" with numerous spaces between the base name and extension. The dialog box displays only the first portion of the filename, making it appear as if the file has a benign extension while actually containing a malicious file type. This technique specifically targets the visual presentation layer rather than the underlying file processing, making it particularly insidious as users are deceived by the interface itself.
The operational impact of this vulnerability extends beyond simple social engineering attacks to potentially enable malicious code execution through various attack vectors. An attacker could send a file disguised as a document or image while it actually contains executable code or malware. The vulnerability aligns with CWE-154 which addresses improper handling of visual representation of data and can be categorized under ATT&CK technique T1059 for execution through deceptive file types. Users who trust the visual representation of files in the Gadu-Gadu interface may unknowingly execute harmful files, particularly when the interface displays the file as a .txt or .doc file while the actual file is a .exe or .bat. The vulnerability essentially undermines the user's ability to make informed decisions about file handling, creating a significant risk for both individual users and organizations that rely on the platform.
Mitigation strategies for this vulnerability must address both the immediate display issues and broader security practices within the Gadu-Gadu client. The primary solution involves implementing proper filename validation that prevents excessive spacing and ensures all file extensions are clearly visible regardless of display limitations. Security measures should include automatic detection of suspicious filename patterns and user warnings when unusual spacing is detected. Additionally, the client should be modified to display the full filename in a separate, non-truncated field or provide a confirmation dialog that explicitly shows the complete file extension. Organizations should also implement network-level filtering to block potentially malicious file types and establish user education programs about the risks of executing files with suspicious extensions. The vulnerability demonstrates the critical importance of defense in depth and highlights that user interface security should not be overlooked in favor of user experience considerations.