CVE-2008-5545 in AntiVirus
Summary
by MITRE
Trend Micro VSAPI 8.700.0.1004 in Trend Micro AntiVirus, when Internet Explorer 6 or 7 is used, allows remote attackers to bypass detection of malware in an HTML document by placing an MZ header (aka "EXE info") at the beginning, and modifying the filename to have (1) no extension, (2) a .txt extension, or (3) a .jpg extension, as demonstrated by a document containing a CVE-2006-5745 exploit.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 10/22/2018
The vulnerability described in CVE-2008-5545 represents a significant bypass mechanism within Trend Micro VSAPI 8.700.0.1004 that affects the detection capabilities of Trend Micro AntiVirus when operating in conjunction with Internet Explorer 6 or 7. This flaw operates at the core of file extension-based detection systems, where the security solution relies on conventional file naming conventions to identify potentially malicious content. The vulnerability specifically targets the way the antivirus engine processes HTML documents that contain embedded executable code, creating a scenario where legitimate security measures can be circumvented through simple file manipulation techniques.
The technical implementation of this vulnerability exploits the fundamental assumption that file extensions serve as reliable indicators of file content and type. When an attacker places an MZ header at the beginning of an HTML document, they are essentially embedding the signature of a Windows executable file within what appears to be a benign web document. The MZ header, which is the standard marker for dos executables, is typically used by operating systems to identify executable files, but when embedded within HTML content and disguised with misleading file extensions, it can confuse the antivirus detection engine. This technique leverages the fact that the VSAPI engine may prioritize file extension analysis over content-based binary signature detection, particularly in older browser environments where file handling behaviors differ from modern standards.
The operational impact of this vulnerability is substantial as it allows threat actors to deliver malware payloads through seemingly harmless web documents that would otherwise be flagged by standard antivirus scanning. The demonstration using CVE-2006-5745 exploit shows how this bypass mechanism can be applied to deliver known vulnerabilities, effectively neutralizing the protection that users expect from their antivirus software. When Internet Explorer 6 or 7 is used in conjunction with this vulnerable Trend Micro version, the attack surface expands significantly as these older browsers had known security limitations and less robust content filtering mechanisms. The vulnerability particularly affects environments where users frequently encounter HTML documents from untrusted sources, making it a serious concern for enterprise security and user protection.
This vulnerability aligns with CWE-427: Uncontrolled Search Path Element and CWE-22: Improper Limitation of a Pathname to a Restricted Directory, as it demonstrates how the system's reliance on predictable file naming conventions can be exploited to bypass security controls. From an ATT&CK framework perspective, this vulnerability maps to T1059.005: Command and Scripting Interpreter: Visual Basic and T1204.002: User Execution: Malicious File, as it enables the delivery and execution of malicious code through user interaction with HTML documents. The attack vector represents a classic case of file extension manipulation that exploits the trust relationship between the operating system and file type associations, where the system's interpretation of file type based on extension leads to incorrect security decisions.
Mitigation strategies for this vulnerability should focus on implementing comprehensive content-based detection mechanisms that do not rely solely on file extensions, particularly in environments where legacy browsers are still in use. Organizations should ensure that antivirus solutions are updated to versions that properly handle embedded binary signatures within non-executable file formats. The recommended approach includes implementing multi-layered detection techniques that combine signature-based detection with behavioral analysis, sandboxing, and heuristic scanning to identify suspicious file content regardless of its apparent file extension. Additionally, user education regarding the risks of opening documents with unusual file extensions and the importance of keeping browser software updated should be emphasized as part of a comprehensive security strategy.