CVE-2005-3229 in Antivir
Summary
by MITRE
Multiple interpretation error in unspecified versions of ClamAV 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 • 07/28/2017
The vulnerability described in CVE-2005-3229 represents a critical flaw in ClamAV antivirus software that demonstrates the complexities of archive file parsing and the potential for bypassing security controls through subtle file format manipulations. This issue specifically affects unspecified versions of ClamAV and exploits a fundamental weakness in how the software interprets RAR archive files, particularly those with malformed central and local headers that maintain structural integrity sufficient to be processed by other archive utilities while simultaneously triggering detection failures in ClamAV's scanning mechanisms.
The technical flaw manifests through a sophisticated interpretation error that occurs during the parsing of RAR archive structures where the central directory and local file headers contain malformed data that violates standard RAR format specifications. However, these malformed headers remain within acceptable ranges for other archive processing tools like WinRAR and PowerZip, which implement more permissive parsing algorithms capable of reconstructing or ignoring the corrupted header information while maintaining functional access to the archive contents. ClamAV's stricter interpretation approach causes it to reject these files as corrupted or invalid, yet this rejection mechanism inadvertently creates a pathway for malicious executables to evade detection.
This vulnerability operates at the intersection of archive format specification compliance and security scanning methodologies, creating a scenario where legitimate archive processing tools and security scanners interpret the same malformed file differently. The operational impact is significant as it allows attackers to craft RAR files that can successfully execute within standard archive utilities while remaining undetected by ClamAV, effectively creating a false sense of security for users relying on this antivirus solution. The attack vector is entirely remote, requiring no local system access or user interaction beyond opening the malicious archive, making it particularly dangerous in email attachment scenarios or file sharing environments.
The flaw demonstrates a classic case of inconsistent security policy enforcement across different software implementations, where the variance in parsing tolerance between different applications creates an exploitable gap in protection. This issue directly relates to CWE-129, which addresses improper validation of input boundaries, and represents a specific instance of how malformed data can be used to bypass security controls through exploitation of parsing differences. From an ATT&CK framework perspective, this vulnerability maps to techniques involving evasion and execution through archive manipulation, specifically targeting defensive measures rather than direct system compromise.
Organizations using ClamAV should immediately implement mitigation strategies including updating to patched versions of the software, implementing additional layers of security such as multiple antivirus solutions, and establishing monitoring for suspicious archive file patterns. The vulnerability highlights the importance of maintaining consistent security policies across different software implementations and the necessity of thorough testing of security tools against malformed inputs. Network administrators should also consider implementing additional file validation mechanisms beyond traditional antivirus scanning, particularly for archive files that may be subject to such interpretation errors, as this represents a fundamental weakness in the security posture that could be exploited in targeted attacks.