CVE-2005-3399 in Quick Heal
Summary
by MITRE
Multiple interpretation error in CAT-QuickHeal 8.0 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 • 07/28/2017
The vulnerability described in CVE-2005-3399 represents a critical file type interpretation flaw in CAT-QuickHeal antivirus software version 8.0 that fundamentally undermines the security model of endpoint protection. This issue stems from the software's improper handling of file magic bytes, specifically the MZ signature that traditionally identifies executable files. The flaw allows attackers to craft malicious files that appear harmless to the antivirus scanner while retaining their executable capabilities, creating a dangerous bypass mechanism that violates fundamental security assumptions about file classification and threat detection.
The technical implementation of this vulnerability exploits the way antivirus engines perform initial file type identification before deeper analysis. When a file contains the MZ magic byte sequence, CAT-QuickHeal's detection logic incorrectly classifies it as a safe file type rather than an executable, despite the file potentially containing multiple embedded content types including executable code. This misclassification occurs because the software's signature recognition system does not properly validate the complete file structure, instead relying on superficial byte patterns that can be manipulated by attackers. The vulnerability specifically affects file types such as BAT, HTML, and EML files, which are commonly encountered in email attachments and web downloads, making the attack vector particularly relevant for enterprise and personal security environments.
The operational impact of this vulnerability extends far beyond simple bypass of antivirus protection, creating a sophisticated attack surface that can be exploited through social engineering and file manipulation techniques. Attackers can create what is termed a "triple headed" program that combines multiple file types within a single payload, where the outer layer appears as a benign HTML or EML file while containing embedded executable content. This approach leverages the principle of file extension and magic byte confusion to evade detection, allowing malicious code to execute on target systems without triggering security alerts. The vulnerability demonstrates a fundamental weakness in the antivirus vendor's approach to file type identification and content validation, potentially enabling code execution, privilege escalation, and data exfiltration attacks.
This vulnerability aligns with several cybersecurity frameworks and threat modeling concepts, including the common weakness enumeration CWE-20, which addresses improper input validation, and represents a clear example of the ATT&CK technique T1059.007 for command and scripting interpreter. The attack pattern follows the typical methodology of using file format confusion to bypass security controls, similar to other magic byte-based attacks that have been documented in various security research publications. Organizations deploying CAT-QuickHeal 8.0 would be particularly vulnerable to attacks that exploit this flaw, as the software's classification system becomes unreliable for determining file safety. The vulnerability also reflects broader challenges in the antivirus industry regarding signature-based detection systems and their susceptibility to format confusion attacks.
Mitigation strategies for this vulnerability should include immediate software updates from the vendor to address the magic byte interpretation flaw, along with enhanced file validation procedures that implement more robust file type identification mechanisms. Organizations should implement additional layers of protection including email filtering, web proxy scanning, and behavioral analysis systems that can detect anomalous file execution patterns regardless of initial classification. Network segmentation and privilege separation measures can help contain potential exploitation attempts, while regular security audits should verify that file handling processes properly validate complete file structures rather than relying on superficial signatures. The incident underscores the critical importance of comprehensive file validation in security software and highlights the need for multi-layered defense approaches that do not depend solely on signature-based detection methods.