CVE-2008-5522 in AVG
Summary
by MITRE
AVG Anti-Virus 8.0.0.161, 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 • 10/22/2018
The vulnerability described in CVE-2008-5522 represents a significant bypass mechanism within AVG Anti-Virus 8.0.0.161 that specifically targets the heuristic analysis capabilities of the security solution when operating in conjunction with Internet Explorer 6 or 7 browsers. This flaw exploits the way antivirus software processes and categorizes file types during web browsing activities, creating a pathway for malicious actors to evade detection of harmful content. The vulnerability operates through a sophisticated manipulation of file headers and naming conventions that fundamentally undermines the antivirus engine's ability to properly identify and classify potentially dangerous files.
The technical implementation of this vulnerability relies on the manipulation of executable file headers by placing an MZ header at the beginning of HTML documents, effectively disguising malicious code as legitimate file types. This technique exploits the inherent limitations of file type detection mechanisms that rely heavily on file extensions and header analysis. When a user accesses a specially crafted HTML document through Internet Explorer 6 or 7, the antivirus system incorrectly interprets the file based on its modified naming convention and header structure. The MZ header, which is the standard marker for executable files in windows operating systems, when combined with filenames lacking extensions or possessing innocuous extensions like .txt or .jpg, creates a deceptive environment where the security solution fails to properly analyze the content.
The operational impact of this vulnerability extends beyond simple detection bypass to encompass broader security implications for users of the affected antivirus solution. Attackers can leverage this flaw to deliver exploits such as CVE-2006-5745, which targets vulnerabilities in Microsoft Office applications, by packaging them within seemingly harmless HTML documents. This creates a multi-layered attack vector that combines social engineering with technical exploitation, allowing malicious actors to bypass multiple security controls simultaneously. The vulnerability is particularly concerning because it affects a widely used antivirus solution and browser combination, potentially exposing large user bases to targeted attacks.
From a cybersecurity perspective, this vulnerability aligns with CWE-119, which addresses weaknesses in memory handling, and demonstrates how improper file type validation can lead to security bypasses. The attack pattern follows principles similar to those documented in MITRE ATT&CK framework under T1059 for command and scripting interpreter and T1203 for Exploitation for Client Execution, where adversaries manipulate file attributes to execute malicious code. The flaw essentially represents a failure in the antivirus solution's file classification and analysis engine, where the system's heuristic capabilities are circumvented through simple but effective file header manipulation. This type of vulnerability highlights the critical importance of comprehensive file analysis that goes beyond simple extension-based detection methods.
Mitigation strategies for this vulnerability require both immediate patching of the affected AVG Anti-Virus version and implementation of enhanced file analysis protocols. Organizations should ensure that all systems running AVG 8.0.0.161 are updated to the latest version that addresses this specific bypass mechanism. Additionally, network administrators should implement additional layers of security including web filtering solutions and enhanced browser security configurations that can detect and block suspicious file attributes regardless of their apparent file type. The vulnerability also underscores the need for security solutions to maintain robust heuristic analysis capabilities that can identify malicious patterns in file headers and content structure, rather than relying solely on extension-based identification methods. Proper security awareness training for users is also essential to recognize potentially malicious documents that may appear legitimate due to their file naming conventions.