CVE-2005-3379 in OfficeScan
Summary
by MITRE
Multiple interpretation error in Trend Micro (1) PC-Cillin 2005 12.0.1244 with the 7.510.1002 engine and (2) OfficeScan 7.0 with the 7.510.1002 engine 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-2005-3379 represents a critical file type interpretation flaw in Trend Micro's antivirus solutions, specifically affecting PC-Cillin 2005 and OfficeScan 7.0 products. This issue stems from improper handling of file magic bytes, which are specific sequences of bytes that identify file formats and help applications determine how to process them. The vulnerability allows attackers to craft malicious files that exploit the software's failure to properly validate file types, creating a dangerous bypass mechanism for virus scanning operations. The flaw specifically manifests when files containing an "MZ" magic byte sequence are processed, which is typically associated with executable files but is incorrectly interpreted by the antivirus software as a safe file type.
The technical implementation of this vulnerability exploits the fundamental principle of file type detection through magic numbers, where the software relies on these byte sequences to determine file classification and subsequent processing. When a file with an "MZ" header is encountered, the antivirus engine incorrectly categorizes it as a safe file type rather than recognizing it as a potential executable threat. This misclassification occurs because the software fails to perform proper file type validation beyond the initial magic byte detection. The vulnerability becomes particularly dangerous when attackers create "triple headed" programs that combine multiple file types within a single container, such as files containing EXE, EML, and HTML content simultaneously. These composite files leverage the magic byte bug to bypass security measures while maintaining their executable capabilities.
The operational impact of this vulnerability extends beyond simple bypass of antivirus protection, creating a significant threat vector for malicious code delivery and execution. Attackers can craft files that appear benign to antivirus software but contain embedded executable code that executes when opened by end-user applications. This creates a multi-layered attack scenario where the initial file appears safe to security tools but can still execute dangerous payloads through legitimate application handlers. The vulnerability affects systems where these specific Trend Micro versions are deployed, potentially allowing attackers to establish persistence, execute arbitrary code, and compromise system integrity without detection. The impact is particularly severe because it undermines the core security premise of antivirus software, which is to identify and neutralize potentially harmful file types before they can be executed.
The flaw aligns with CWE-20, "Improper Input Validation," and demonstrates how inadequate validation of file format identification can create security vulnerabilities. From an ATT&CK framework perspective, this vulnerability maps to T1059.001 "Command and Scripting Interpreter: PowerShell" and T1204.002 "User Execution: Malicious File" as it enables attackers to deliver malicious files that bypass initial security checks. The vulnerability also relates to T1566 "Phishing" and T1078 "Valid Accounts" as it allows attackers to craft files that appear legitimate to security tools while still executing malicious code. Organizations using affected Trend Micro versions should implement immediate mitigations including software updates, enhanced file type validation, and additional security layers such as application whitelisting and network-based protections. The vulnerability highlights the importance of proper file format validation and the need for security solutions to maintain robust detection mechanisms that cannot be easily bypassed through simple magic byte manipulation.