CVE-2008-5537 in Pctools Antivirus
Summary
by MITRE
PC Tools AntiVirus 4.4.2.0, 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.
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Analysis
by VulDB Data Team • 11/28/2017
The vulnerability described in CVE-2008-5537 represents a significant bypass mechanism within PC Tools AntiVirus 4.4.2.0 that exploits the way security software handles file type detection and malware analysis. This flaw specifically targets the interaction between the antivirus solution and Microsoft Internet Explorer versions 6 and 7, creating a pathway for attackers to evade detection of malicious content through simple file manipulation techniques. The vulnerability operates at the intersection of file extension handling, content inspection, and security policy enforcement, making it particularly concerning for enterprise environments where legacy browsers and antivirus solutions remain in use.
The technical implementation of this vulnerability relies on the manipulation of executable file headers and filename extensions to deceive antivirus engines into treating malicious content as benign files. When an attacker places an MZ header - which is the standard signature for windows executable files - at the beginning of an HTML document, the antivirus software may incorrectly interpret the file as an executable rather than an HTML document. This technique exploits the fact that many antivirus solutions perform content analysis based on file extensions and headers, with the MZ signature being a strong indicator of executable files that should trigger immediate security alerts. The attack vector becomes particularly effective when the filename is modified to remove its extension entirely, or to use extensions like .txt or .jpg, which are commonly associated with benign content.
The operational impact of this vulnerability extends beyond simple detection bypass, as it demonstrates a fundamental weakness in how legacy antivirus solutions handle file classification and content inspection. This weakness allows attackers to craft documents that appear harmless to users while containing sophisticated malware payloads that can exploit known vulnerabilities such as CVE-2006-5745. The combination of this bypass technique with existing exploits creates a dangerous scenario where users might encounter documents that appear to be simple text files or images but contain executable code capable of executing arbitrary commands on the target system. This vulnerability particularly affects environments where users frequently interact with HTML documents through older versions of Internet Explorer, which were notorious for their security shortcomings and limited sandboxing capabilities.
The security implications of CVE-2008-5537 align with common attack patterns documented in the attack framework, specifically relating to file extension manipulation and content deception techniques that are often categorized under CWE-15 (External Control of System or Configuration Setting) and CWE-20 (Improper Input Validation). This vulnerability represents a classic example of how insufficient input validation and improper file type handling can lead to security bypass scenarios. Organizations using outdated antivirus solutions like PC Tools AntiVirus 4.4.2.0 face significant risk from this vulnerability, as the bypass mechanism requires minimal technical expertise to implement and can be easily automated. The attack surface is further expanded by the fact that many organizations continue to support older browser versions, creating a persistent threat vector that can be exploited across multiple systems.
Mitigation strategies for this vulnerability should focus on immediate solution upgrades and configuration changes to address the underlying detection flaws. Organizations must upgrade to modern antivirus solutions that properly handle file content inspection regardless of filename extensions, implementing signature-based detection combined with behavioral analysis to identify malicious activities. Network administrators should configure browsers to disable automatic execution of potentially malicious content, particularly in environments where older Internet Explorer versions remain in use. The implementation of strict file extension policies and content inspection rules can help prevent the execution of files with suspicious headers even when they appear to be benign. Additionally, regular security assessments should verify that antivirus solutions are properly configured to handle various file type scenarios and that legacy systems are either updated or properly isolated from critical network resources. This vulnerability underscores the importance of maintaining current security solutions and the dangers of relying on outdated security software that may not properly address evolving attack techniques.