CVE-2008-5533 in AntiVirus
Summary
by MITRE
K7AntiVirus 7.10.541 and possibly 7.10.454, 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-2008-5533 represents a significant security flaw in K7AntiVirus version 7.10.541 and potentially 7.10.454, specifically affecting detection capabilities when Internet Explorer 6 or 7 is in use. This issue stems from a fundamental weakness in the antivirus software's file extension and header analysis mechanisms, creating a bypass opportunity for sophisticated malware delivery methods. The flaw exploits the way the antivirus engine processes file identification, particularly when dealing with HTML documents that contain embedded malicious payloads, demonstrating a critical gap in heuristic and signature-based detection systems.
The technical implementation of this vulnerability relies on the manipulation of file headers and naming conventions to evade detection mechanisms. Attackers can place an MZ header at the beginning of an HTML document, which is the characteristic signature of executable files, while simultaneously altering the filename extension to appear as a benign text or image file. This technique specifically targets the filename extension checking functionality within the antivirus software, where the system fails to properly analyze the actual file content and instead relies on superficial indicators. The MZ header, which stands for Mark Zbikowski, is the standard signature for windows executable files and typically triggers immediate detection in properly functioning antivirus systems, but this bypass allows it to remain undetected when disguised as other file types.
The operational impact of this vulnerability extends beyond simple malware evasion, creating a dangerous precedent for user trust and system security. When Internet Explorer 6 or 7 is used in conjunction with the vulnerable K7AntiVirus version, users face increased exposure to malicious content that could include exploits such as CVE-2006-5745, which targets vulnerabilities in the Windows operating system. This bypass mechanism essentially allows attackers to create seemingly harmless documents that contain sophisticated malware payloads, exploiting the trust users place in their antivirus protection. The vulnerability demonstrates how improper file type detection can lead to complete security system compromise, particularly in environments where legacy browsers are still in use.
This vulnerability aligns with CWE-20, which describes improper input validation, and reflects a classic example of how insufficient content analysis can lead to security bypasses. The attack vector specifically targets the principle of least privilege and defense in depth, as it allows malicious content to bypass multiple layers of security controls that should prevent execution of harmful code. From an ATT&CK framework perspective, this vulnerability maps to techniques involving social engineering and execution through exploitation of trust relationships, where the malicious document appears legitimate due to its disguised file extension while containing the actual malicious payload. The bypass mechanism also relates to TTPs involving fileless malware delivery and command and control communications that rely on user interaction with infected documents. Organizations using vulnerable versions of K7AntiVirus face significant risk of successful phishing campaigns and targeted attacks, particularly in environments where users regularly interact with HTML documents and legacy browser environments. The recommended mitigations include immediate software updates, implementation of additional content inspection layers, and user education regarding suspicious document behavior regardless of file extensions.