CVE-2005-3376 in Kaspersky Anti-virus
Summary
by MITRE
Multiple interpretation error in Kaspersky 5.0.372 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 • 07/26/2017
The vulnerability identified as CVE-2005-3376 represents a critical file type interpretation flaw in Kaspersky Anti-Virus version 5.0.372 that fundamentally undermines the software's ability to properly categorize and scan potentially malicious files. This issue stems from the software's improper handling of file magic bytes, specifically the MZ signature that traditionally identifies executable files. The vulnerability allows attackers to craft files that appear benign to the antivirus scanner while containing malicious payloads that can execute with full system privileges.
The technical nature of this flaw places it squarely within CWE-20, which describes improper input validation, and more specifically aligns with CWE-1104, related to the use of a magic number with inappropriate usage. The vulnerability exploits the fact that Kaspersky's scanning engine relies on magic byte detection to determine file types, and when it encounters an MZ signature at the beginning of files such as BAT, HTML, or EML, it incorrectly classifies these files as safe. This misclassification occurs because the scanner's heuristic analysis fails to properly validate the file's actual content against its claimed type, creating a dangerous gap in the security posture.
The operational impact of this vulnerability is particularly severe as it enables attackers to create what researchers have termed "triple headed" programs that combine multiple file types into a single malicious payload. These composite files contain EXE, EML, and HTML content simultaneously, with the MZ signature causing the antivirus to treat the entire file as a safe type despite its dangerous capabilities. This approach allows attackers to bypass security controls that would normally detect and quarantine executable content, effectively rendering the antivirus protection ineffective against such sophisticated attacks.
This vulnerability directly relates to several tactics in the MITRE ATT&CK framework, particularly those involving execution through masquerading and privilege escalation. The technique of using magic bytes to disguise malicious files aligns with ATT&CK tactic T1036, which covers masquerading and spoofing techniques. Additionally, the ability to execute dangerous content through seemingly safe file types supports ATT&CK technique T1059, covering command and scripting interpreter execution. The vulnerability also enables persistent threats through T1078, which covers valid accounts and legitimate credentials usage, as the malicious file can execute with the privileges of the user who opens it.
Mitigation strategies for CVE-2005-3376 require immediate software updates to the latest Kaspersky Anti-Virus versions that properly implement magic byte validation and file type detection. Organizations should implement layered security approaches including network-based intrusion detection systems, application whitelisting, and strict file type validation at network boundaries. System administrators should also consider implementing behavioral monitoring tools that can detect unusual execution patterns, as the vulnerability may allow attackers to execute malicious code without triggering traditional signature-based detection mechanisms. Additionally, user education programs should emphasize the importance of avoiding suspicious files, particularly those with unusual extensions or those that appear to be multiple file types simultaneously. The vulnerability highlights the critical importance of robust file validation mechanisms and proper input sanitization in security software, as it demonstrates how a single flawed assumption about file identification can compromise an entire security infrastructure.