CVE-2005-3375 in Ikarus Antivirus
Summary
by MITRE
Multiple interpretation error in Ikarus demo version allows remote attackers to bypass virus scanning via a file such as BAT, HTML, and EML with an "MZ" magic byte sequence which is normally associated with EXE, which causes the file to be treated as a safe type that could still be executed as a dangerous file type by applications on the end system, as demonstrated by a "triple headed" program that contains EXE, EML, and HTML content, aka the "magic byte bug."
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Analysis
by VulDB Data Team • 07/29/2017
The CVE-2005-3375 vulnerability represents a critical file type interpretation flaw in the Ikarus antivirus demo version that fundamentally undermines the security posture of endpoint protection systems. This vulnerability stems from the software's improper handling of file magic bytes, specifically the MZ signature that traditionally identifies executable files. The flaw allows attackers to craft malicious files that appear benign to the antivirus scanner but retain executable capabilities when processed by the operating system, creating a dangerous bypass mechanism for malware delivery. The vulnerability is particularly concerning because it exploits the trust relationship between antivirus software and file type identification, enabling attackers to circumvent security controls that rely on accurate file classification.
The technical implementation of this vulnerability involves the manipulation of file headers to deceive the Ikarus scanner into treating malicious files as safe types. When a file containing an MZ magic byte sequence is presented to the system, the scanner incorrectly interprets its type and applies less restrictive scanning rules. This misinterpretation occurs because the demo version fails to properly validate file signatures against their actual content, instead relying on superficial header matching. The vulnerability specifically affects file types such as BAT, HTML, and EML files that can be crafted to contain embedded EXE content while maintaining the deceptive MZ signature that triggers the false positive in the antivirus engine. The "triple headed" program demonstration showcases how attackers can combine multiple file types within a single payload, leveraging the magic byte bug to execute malicious code through seemingly harmless file extensions.
The operational impact of CVE-2005-3375 extends beyond simple bypass of antivirus protection, creating a significant risk for endpoint systems that rely on Ikarus for security. When attackers exploit this vulnerability, they can deliver malware that executes with elevated privileges and bypasses traditional security controls designed to prevent execution of malicious code. The vulnerability affects systems where the Ikarus demo version is installed, potentially allowing attackers to execute malicious payloads through email attachments, web downloads, or file transfers. The risk is compounded by the fact that the demo version typically lacks the comprehensive scanning capabilities of full commercial versions, making the system more vulnerable to exploitation. This vulnerability aligns with CWE-156, which addresses improper handling of input validation, and represents a classic case of insufficient input sanitization that allows attackers to manipulate system behavior through crafted file headers.
The exploitation of this vulnerability demonstrates a sophisticated understanding of file format structures and antivirus evasion techniques. Attackers can craft files that appear to be safe text-based formats like HTML or EML while containing executable code that executes when opened or processed by the system. The vulnerability creates a persistent threat vector because it operates at the file type detection level rather than the payload execution level, meaning that even if the malware payload is detected later, the initial bypass has already occurred. This type of vulnerability is particularly dangerous in enterprise environments where antivirus systems are expected to provide comprehensive protection against all file types. The ATT&CK framework categorizes this as a technique for privilege escalation and defense evasion, as it allows adversaries to bypass security controls that would normally prevent execution of malicious code. Organizations using Ikarus demo versions face significant exposure to this vulnerability, as it essentially provides a backdoor mechanism for attackers to execute malicious code without triggering appropriate security alerts. The vulnerability also highlights the importance of proper file type validation and signature verification in security software, emphasizing the need for robust input validation mechanisms that prevent header-based deception attacks.