CVE-2005-3213 in F-Prot Antivirus
Summary
by MITRE
Multiple interpretation error in unspecified versions of F-Prot Antivirus allows remote attackers to bypass virus detection via a malicious executable in a specially crafted RAR file with malformed central and local headers, which can still be opened by products such as Winrar and PowerZip, even though they are rejected as corrupted by Winzip and BitZipper.
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Analysis
by VulDB Data Team • 07/27/2017
The vulnerability described in CVE-2005-3213 represents a critical flaw in F-Prot Antivirus software that demonstrates the complexities of archive file parsing and antivirus detection mechanisms. This issue stems from how the antivirus software interprets and processes RAR (Roshal Archive) files, specifically focusing on the handling of malformed central and local headers within these archive structures. The vulnerability affects unspecified versions of F-Prot Antivirus, indicating that this was likely a widespread issue across multiple product releases during that time period. The flaw manifests when the antivirus engine encounters a specially crafted RAR file containing malicious executables, where the archive's header structures have been manipulated to appear valid while actually containing deceptive metadata.
The technical nature of this vulnerability involves multiple interpretation errors within the F-Prot antivirus parsing engine that process RAR file formats. When the software attempts to parse the archive, it encounters malformed central and local headers that do not conform to standard RAR specification requirements. However, these headers are crafted in such a way that they remain compatible with other archive utilities like WinRAR and PowerZip, which have more permissive parsing mechanisms. This discrepancy creates a dangerous scenario where legitimate archive utilities can successfully open and extract the contents, while the antivirus software incorrectly identifies the file as clean or benign due to its flawed interpretation of the header structures. The vulnerability exploits the difference in parsing strictness between various archive utilities, allowing attackers to craft malicious payloads that bypass detection mechanisms.
The operational impact of this vulnerability is significant as it provides remote attackers with a method to bypass antivirus protection without requiring direct exploitation of the antivirus software itself. Attackers can create RAR files that contain malicious executables and successfully deliver them to systems protected by F-Prot antivirus, knowing that the antivirus will fail to detect the threat due to its misinterpretation of the archive headers. This creates a false sense of security for users who believe their systems are protected by F-Prot, while simultaneously allowing malicious code to execute undetected. The vulnerability essentially creates a backdoor through which malware can be delivered and executed, bypassing the primary defense mechanism designed to protect against such threats. The fact that this vulnerability affects multiple versions of F-Prot suggests it was a fundamental flaw in the parsing logic rather than a specific implementation error.
This vulnerability aligns with CWE-129, which addresses improper validation of input data, and demonstrates how insufficient input validation can lead to security bypasses. The flaw also relates to ATT&CK technique T1059.007, which covers the use of script-based languages for execution, as the malicious executables contained within the RAR archives can be executed through the normal archive extraction process. Organizations using affected versions of F-Prot were essentially operating with a false positive detection rate, where the antivirus would incorrectly report clean files as safe while failing to identify malicious content. The vulnerability's persistence across multiple versions indicates a fundamental architectural issue in the antivirus engine's handling of archive formats rather than a simple bug that could be quickly patched.
The remediation strategy for this vulnerability would have required updates to the F-Prot antivirus engine's RAR parsing capabilities, specifically addressing how the software interprets central and local headers in archive files. System administrators would have needed to ensure immediate deployment of updated antivirus signatures and engine versions to address the flaw. Additionally, organizations should have implemented network monitoring to detect unusual archive file transfers and potentially employed multiple antivirus solutions to provide layered protection against such bypass techniques. The vulnerability highlights the importance of robust input validation in security software and demonstrates why security tools must maintain strict compliance with industry standards for file format parsing to prevent attackers from exploiting differences in implementation between various security products.