CVE-2005-3401 in TheHacker
Summary
by MITRE
Multiple interpretation error in TheHacker 5.8.4.128 allows remote attackers to bypass virus scanning via a file such as BAT, HTML, and EML with an "MZ" magic byte sequence which is normally associated with EXE, which causes the file to be treated as a safe type that could still be executed as a dangerous file type by applications on the end system, as demonstrated by a "triple headed" program that contains EXE, EML, and HTML content, aka the "magic byte bug."
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Analysis
by VulDB Data Team • 07/12/2018
The vulnerability described in CVE-2005-3401 represents a critical file type interpretation error that affects TheHacker 5.8.4.128 antivirus software. This flaw stems from the software's improper handling of file magic bytes, specifically the MZ signature that traditionally identifies executable files. The issue arises when the antivirus system encounters files with MZ magic bytes in non-executable formats such as BAT, HTML, or EML files. This misinterpretation allows malicious actors to craft files that appear benign to the antivirus scanner while retaining executable capabilities, creating a dangerous bypass mechanism.
The technical implementation of this vulnerability exploits the fundamental principle of file type detection based on magic numbers or signature bytes. When TheHacker software encounters a file with MZ magic bytes, it incorrectly classifies the file as safe due to its association with executable formats, despite the file's actual content being in a different format. This misclassification occurs because the antivirus engine prioritizes the magic byte detection over other file analysis methods, leading to a false positive in the safety assessment. The vulnerability specifically affects the software's file type recognition algorithm, which fails to properly validate the actual file content against its reported type, creating a mismatch that attackers can exploit.
The operational impact of this vulnerability is severe and multifaceted, as it enables attackers to deliver malicious code that bypasses traditional antivirus protection mechanisms. The demonstration of a "triple headed" program illustrates how a single file can contain multiple payload types, with the MZ signature allowing the system to treat it as a safe executable while the underlying content remains potentially harmful. This creates a vector for code execution attacks where the malicious file can be delivered through email attachments, web downloads, or other common attack vectors. The vulnerability essentially allows for the creation of polymorphic malware that can evade detection by relying on the antivirus software's own misinterpretation of file signatures.
This vulnerability aligns with CWE-1009, which addresses improper handling of multiple representations of data, and represents a classic case of signature-based detection failure. The flaw demonstrates the importance of proper input validation and the dangers of relying solely on magic byte detection without comprehensive file analysis. From an ATT&CK framework perspective, this vulnerability maps to technique T1059.007 for command and scripting interpreter and T1566 for phishing, as attackers can leverage this bypass to deliver malicious payloads through seemingly legitimate file types. The vulnerability also relates to T1070.004 for indicator removal, as the malicious file can evade detection while maintaining its execution capabilities.
Mitigation strategies for this vulnerability should focus on implementing more robust file type identification methods that do not rely solely on magic bytes. Organizations should ensure that TheHacker software is updated to versions that properly validate file content against reported types and implement additional layers of file analysis beyond simple signature detection. The recommended approach includes deploying multiple antivirus solutions with different detection methodologies, implementing strict file type validation policies, and establishing comprehensive monitoring for suspicious file behavior. Additionally, security teams should consider implementing sandboxing mechanisms that can execute suspicious files in isolated environments to detect malicious behavior regardless of file type detection errors, as this vulnerability fundamentally breaks the trust model between file type identification and actual security assessment.