CVE-2007-3122 in ClamAV
Summary
by MITRE
The parsing engine in ClamAV before 0.90.3 and 0.91 before 0.91rc1 allows remote attackers to bypass scanning via a RAR file with a header flag value of 10, which can be processed by WinRAR.
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Analysis
by VulDB Data Team • 07/20/2021
The vulnerability described in CVE-2007-3122 represents a critical flaw in the ClamAV antivirus software's file parsing mechanism that specifically affects versions prior to 0.90.3 and 0.91rc1. This issue stems from an insufficient validation process within ClamAV's RAR file handling capabilities, creating a significant security gap that adversaries can exploit to evade detection. The vulnerability is particularly concerning because it allows attackers to craft malicious RAR archives that bypass the antivirus scanning process entirely, undermining the fundamental purpose of antivirus protection systems.
The technical root cause of this vulnerability lies in ClamAV's parsing engine failing to properly validate RAR file header flag values during the decompression process. When a RAR file contains a header flag value of 10, the system incorrectly processes this specific flag, causing ClamAV to skip scanning the contents of the archive entirely. This behavior occurs because the parsing engine does not adequately check the integrity of RAR file headers, particularly those with non-standard flag values that are valid according to the RAR specification but are not properly handled by ClamAV's detection logic. The vulnerability demonstrates a classic case of insufficient input validation where the software accepts and processes malformed or non-standard file structures without proper sanitization.
The operational impact of this vulnerability extends beyond simple evasion of antivirus detection, as it creates a persistent security risk for systems running vulnerable versions of ClamAV. Attackers can exploit this weakness by creating specially crafted RAR archives that contain malicious payloads, knowing that these files will bypass scanning mechanisms that should detect and quarantine them. This vulnerability directly impacts the security posture of organizations relying on ClamAV for malware detection, potentially allowing zero-day exploits to reach target systems undetected. The attack vector is particularly dangerous because RAR files are commonly used for legitimate file compression and distribution, making the evasion technique more likely to succeed in real-world scenarios where users might not suspect compressed files of containing malicious content.
From a cybersecurity framework perspective, this vulnerability aligns with CWE-20, which describes improper input validation, and represents a failure in the software's defensive mechanisms against malformed inputs. The issue also maps to ATT&CK technique T1059.007, which involves the use of RAR archives as a method for executing malicious code. Organizations affected by this vulnerability should immediately implement mitigation strategies including updating to ClamAV versions 0.90.3 or later, implementing network-based monitoring for suspicious RAR file activity, and establishing additional layers of security controls such as application whitelisting. The vulnerability highlights the importance of robust input validation in security software and demonstrates why regular updates and patch management are critical components of enterprise security strategies. Additionally, system administrators should consider implementing file type restrictions and enhanced monitoring for compressed file extraction activities to detect potential exploitation attempts.