CVE-2020-3327 in ClamAV
Summary
by MITRE
A vulnerability in the ARJ archive parsing module in Clam AntiVirus (ClamAV) Software versions 0.102.2 could allow an unauthenticated, remote attacker to cause a denial of service condition on an affected device. The vulnerability is due to a heap buffer overflow read. An attacker could exploit this vulnerability by sending a crafted ARJ file to an affected device. An exploit could allow the attacker to cause the ClamAV scanning process crash, resulting in a denial of service condition.
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Analysis
by VulDB Data Team • 10/18/2020
The vulnerability identified as CVE-2020-3327 represents a critical heap buffer overflow read flaw within the ARJ archive parsing functionality of Clam AntiVirus software version 0.102.2. This issue resides in the core scanning module responsible for processing archive files, specifically targeting the ARJ format parser that handles compressed file structures used in various malware distribution channels. The vulnerability stems from inadequate bounds checking during the parsing of maliciously crafted ARJ archives, creating an exploitable condition that can be leveraged by remote attackers without requiring authentication credentials. The flaw manifests when the software attempts to read data beyond the allocated heap buffer boundaries, leading to memory corruption that fundamentally compromises the stability of the scanning process. This type of vulnerability falls under the CWE-125 weakness category, specifically addressing out-of-bounds read conditions that occur when software accesses memory locations beyond the intended buffer limits. The attack vector is particularly concerning as it enables remote exploitation through simple file delivery mechanisms, making it accessible to adversaries who may not require direct system access or elevated privileges to execute successful attacks. The ARJ format parsing module in ClamAV demonstrates insufficient input validation and memory management controls, creating a pathway for attackers to manipulate the software's memory structures through carefully constructed malicious archives.
The operational impact of CVE-2020-3327 extends beyond simple service disruption, as it fundamentally undermines the reliability and effectiveness of antivirus protection mechanisms that depend on ClamAV's scanning capabilities. When exploited successfully, the heap buffer overflow causes the ClamAV scanning process to terminate abruptly, resulting in immediate denial of service conditions that can affect entire network infrastructures relying on this protection layer. The vulnerability's remote nature means that attackers can potentially compromise protection systems without physical access to target devices, making it particularly dangerous in enterprise environments where multiple systems may be scanning incoming files through centralized ClamAV instances. This condition creates a cascading effect where legitimate security operations are disrupted, potentially leaving systems vulnerable to other threats during the service interruption period. The DoS condition affects both individual workstation scanning and network-wide file inspection capabilities, as the crash occurs at the core scanning engine level rather than in peripheral components. Organizations utilizing ClamAV for email filtering, file system monitoring, or endpoint protection may experience complete service outages, forcing administrators to manually restart services and potentially delaying critical security operations. The vulnerability's exploitation does not require complex attack chains or privilege escalation, making it particularly attractive to threat actors seeking to disrupt security infrastructure without sophisticated technical capabilities.
Mitigation strategies for CVE-2020-3327 must address both immediate remediation and long-term security posture improvements to protect against similar vulnerabilities in archive parsing modules. The primary and most effective mitigation involves upgrading to ClamAV versions that contain patches addressing this specific heap buffer overflow condition, typically found in versions released after the vulnerability disclosure. Organizations should implement immediate patch management procedures to ensure all affected systems receive updates without delay, particularly focusing on critical infrastructure and network scanning points where ClamAV services are actively deployed. Network administrators should consider implementing additional file validation layers that can detect and quarantine suspicious archive files before they reach the ClamAV scanning engine, providing defense-in-depth protection. The vulnerability highlights the importance of input validation and memory safety practices, suggesting that organizations should review their software supply chain for similar buffer overflow conditions in other archive parsing libraries or security tools. Implementing automated monitoring for service crashes and unusual scanning behavior can help detect exploitation attempts, while maintaining detailed logs of file scanning activities enables forensic analysis if attacks occur. Security teams should also consider temporarily disabling ARJ archive scanning capabilities in affected systems until proper patches are deployed, though this approach reduces overall protection coverage. The incident underscores the necessity of following secure coding practices such as those outlined in the CERT Secure Coding Standards, particularly in areas related to buffer management and input validation, to prevent similar vulnerabilities from emerging in future software releases.