CVE-2019-1785 in ClamAV
Summary
by MITRE
A vulnerability in the RAR file scanning functionality of Clam AntiVirus (ClamAV) Software versions 0.101.1 and 0.101.0 could allow an unauthenticated, remote attacker to cause a denial of service condition on an affected device. The vulnerability is due to a lack of proper error-handling mechanisms when processing nested RAR files sent to an affected device. An attacker could exploit this vulnerability by sending a crafted RAR file to an affected device. An exploit could allow the attacker to view or create arbitrary files on the targeted system.
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Analysis
by VulDB Data Team • 08/27/2023
The vulnerability identified as CVE-2019-1785 represents a critical denial of service weakness within Clam AntiVirus software versions 0.101.1 and 0.101.0, specifically affecting the RAR file scanning functionality. This flaw manifests when the antivirus system processes nested RAR archives, creating a scenario where improper error handling leads to system instability. The vulnerability stems from inadequate input validation and exception management during the decompression and analysis of compressed file structures, particularly when encountering malformed or specially crafted RAR archives that contain nested compression layers.
The technical exploitation of this vulnerability occurs through the manipulation of RAR file structures that contain multiple layers of compression, where each layer may contain additional compressed content. When ClamAV attempts to process these nested archives without proper safeguards against malformed data or recursive compression anomalies, the software enters an undefined state where memory management fails or processing loops occur. This condition results in the application crashing or becoming unresponsive, effectively causing a denial of service that prevents legitimate security scanning operations from completing successfully.
From an operational perspective, this vulnerability presents significant risk to organizations relying on ClamAV for email filtering, file system scanning, or network security monitoring. The remote exploitation capability means attackers can trigger the denial of service condition without requiring authentication or physical access to the target system, making it particularly dangerous in networked environments. Additionally, the vulnerability's potential to allow arbitrary file creation or viewing represents a secondary security concern that could enable further exploitation attempts, including privilege escalation or data exfiltration activities that extend beyond simple service disruption.
The flaw aligns with CWE-248, an unspecified error in the software's error handling mechanisms, and demonstrates characteristics consistent with the ATT&CK technique T1499.004 for network denial of service. Organizations should implement immediate mitigations including upgrading to ClamAV versions 0.101.2 or later where this vulnerability has been patched, applying network-based filtering to block suspicious RAR files, and implementing additional monitoring for abnormal scanning behavior. The vulnerability also highlights the importance of proper input validation in security software and demonstrates the critical need for robust error handling in decompression routines that process user-supplied content.