CVE-2020-3123 in ClamAV
Summary
by MITRE
A vulnerability in the Data-Loss-Prevention (DLP) module in Clam AntiVirus (ClamAV) Software versions 0.102.1 and 0.102.0 could allow an unauthenticated, remote attacker to cause a denial of service condition on an affected device. The vulnerability is due to an out-of-bounds read affecting users that have enabled the optional DLP feature. An attacker could exploit this vulnerability by sending a crafted email 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 • 03/28/2024
The vulnerability identified as CVE-2020-3123 represents a critical security flaw within the ClamAV antivirus software ecosystem, specifically targeting the Data-Loss-Prevention module that was introduced in versions 0.102.0 and 0.102.1. This issue manifests as an out-of-bounds read condition that fundamentally compromises the stability of the scanning process when the DLP feature is actively enabled. The vulnerability's impact extends beyond simple functionality degradation, creating a potential vector for denial of service attacks that could severely disrupt network security operations. Organizations relying on ClamAV for email scanning and content filtering face significant risk when this vulnerability remains unaddressed, as the flaw can be exploited remotely without authentication requirements.
The technical nature of this vulnerability stems from improper input validation within the DLP module's processing pipeline, where the software fails to adequately verify the boundaries of data structures during email content analysis. This out-of-bounds read condition occurs specifically when analyzing crafted email files that contain malformed or specially constructed content designed to trigger memory access violations. The flaw operates at the application layer and leverages the DLP feature's capability to examine email headers, body content, and attachments, making it particularly dangerous in email security contexts where large volumes of potentially malicious content are processed. The vulnerability's classification aligns with CWE-125, which describes out-of-bounds read conditions, and demonstrates how feature-specific implementations can introduce unexpected security weaknesses even in well-established security software.
The operational impact of CVE-2020-3123 extends far beyond a simple service disruption, creating cascading effects within email security infrastructures that could compromise entire network defense mechanisms. When exploited successfully, the vulnerability forces the ClamAV scanning process to crash, effectively removing the system from active protection and creating a window of vulnerability for actual malware delivery. This denial of service condition can be particularly devastating in enterprise environments where email security appliances and gateway systems rely on ClamAV for real-time threat detection. The attack vector through crafted email files makes this vulnerability particularly insidious as it can be delivered through normal email traffic without requiring special privileges or authentication, allowing adversaries to systematically disable security controls across multiple systems. The potential for this vulnerability to be weaponized in larger attack campaigns against email infrastructure aligns with tactics described in the ATT&CK framework under initial access and execution phases.
Organizations must implement immediate mitigation strategies to address this vulnerability, beginning with the urgent deployment of patched ClamAV versions that resolve the out-of-bounds read condition in the DLP module. System administrators should disable the DLP feature entirely if it is not essential for their security operations, as this provides an immediate workaround while more permanent patches are deployed. Network monitoring should be enhanced to detect unusual scanning process behavior or repeated service crashes that might indicate exploitation attempts. The vulnerability's characteristics make it particularly suitable for reconnaissance activities where attackers might attempt to identify vulnerable systems before launching more sophisticated attacks. Security teams should also consider implementing email content filtering rules that can detect and quarantine suspicious email patterns that might be designed to trigger this specific vulnerability, providing an additional layer of protection against exploitation attempts.