CVE-2008-5536 in Panda Antivirus
Summary
by MITRE
Panda Antivirus 9.0.0.4, 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 • 12/02/2017
The vulnerability described in CVE-2008-5536 represents a significant sandboxing bypass in Panda Antivirus version 9.0.0.4 that specifically targets the interaction between the antivirus software and Internet Explorer 6 or 7 browsers. This flaw exploits the way the antivirus engine processes file types and examines file headers, creating a pathway for malicious actors to circumvent security controls through simple file manipulation techniques. The vulnerability operates at the intersection of file extension handling, binary signature detection, and browser-based execution contexts, making it particularly dangerous in enterprise environments where users frequently interact with web content through older browser versions.
The technical mechanism behind this vulnerability involves the manipulation of executable file headers and filename extensions to deceive the antivirus detection system. When an attacker places an MZ header at the beginning of an HTML document, they are essentially creating a file that appears to be an executable binary, since the MZ header is the standard marker for dos executable files. The antivirus system, when processing the file through Internet Explorer, fails to properly validate the file type based on its actual content rather than its extension. This allows the system to treat a malicious HTML document as if it were a legitimate executable file, bypassing the normal detection mechanisms that would otherwise identify the threat.
The operational impact of this vulnerability is substantial as it demonstrates how attackers can leverage the trust placed in file extension validation to execute malicious code. By simply renaming files to have no extension, .txt extensions, or .jpg extensions, attackers can create documents that appear benign to users while containing hidden executable content. The specific exploitation of CVE-2006-5745 demonstrates that this bypass can be used to deliver more sophisticated attacks, potentially leading to full system compromise. This vulnerability particularly affects organizations using older versions of Internet Explorer, which were common in enterprise environments during that time period, creating a significant attack surface.
This vulnerability aligns with CWE-20, "Improper Input Validation," and represents a classic case of insufficient validation of file type and content. The attack pattern follows the techniques outlined in the ATT&CK framework under T1059.005 for command and scripting interpreter, as well as T1204.002 for user execution through social engineering. The bypass mechanism is particularly concerning because it exploits the fundamental assumption that file extensions accurately represent file content, a principle that many security systems rely upon for proper threat detection and classification.
Organizations should implement multiple layers of defense to mitigate this vulnerability, including strict file extension validation, enhanced content inspection beyond simple header analysis, and mandatory updates to modern browser versions that do not exhibit this behavior. Network-based security controls should be configured to inspect file content regardless of extension, and user education programs should emphasize the importance of not executing files with suspicious extensions or from untrusted sources. Additionally, security policies should mandate that antivirus systems perform comprehensive content analysis rather than relying solely on file extension-based detection, ensuring that files are properly classified based on their actual content rather than their proposed type.