CVE-2019-1787 in ClamAV
Summary
by MITRE
A vulnerability in the Portable Document Format (PDF) scanning functionality of Clam AntiVirus (ClamAV) Software versions 0.101.1 and prior could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. The vulnerability is due to a lack of proper data handling mechanisms within the device buffer while indexing remaining file data on an affected device. An attacker could exploit this vulnerability by sending crafted PDF files to an affected device. A successful exploit could allow the attacker to cause a heap buffer out-of-bounds read condition, resulting in a crash that could result in a denial of service condition on an affected device.
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Analysis
by VulDB Data Team • 08/27/2023
The vulnerability identified as CVE-2019-1787 resides within the Portable Document Format scanning capabilities of Clam AntiVirus software, specifically affecting versions 0.101.1 and earlier. This weakness manifests in the improper handling of data within device buffers during the indexing process of remaining file data, creating a critical security gap that adversaries can exploit to disrupt system operations. The flaw fundamentally lies in the software's inability to properly validate and manage buffer boundaries when processing PDF documents, particularly those containing crafted malicious content designed to trigger specific memory access patterns.
The technical implementation of this vulnerability stems from insufficient input validation mechanisms within the PDF parsing engine of ClamAV. When processing PDF files, the software fails to adequately check buffer limits during the indexing of file data, leading to heap buffer out-of-bounds read conditions. This occurs because the application does not properly enforce boundary checks when allocating and accessing memory regions intended to store PDF document data. The flaw specifically affects the way the software handles remaining file data during scanning operations, where maliciously crafted PDF elements can cause the buffer management system to access memory locations beyond allocated boundaries.
The operational impact of this vulnerability extends beyond simple system disruption, as it creates a vector for remote denial of service attacks that can compromise the availability of security services. An unauthenticated attacker can exploit this weakness by simply sending specially crafted PDF files to a vulnerable ClamAV instance, requiring no privileged access or complex attack infrastructure. The resulting heap buffer overflow condition typically manifests as application crashes, which can be repeatedly triggered to maintain persistent service disruption. This vulnerability directly impacts the reliability of antivirus scanning services, potentially leaving systems vulnerable to other threats during the periods of service unavailability.
From a cybersecurity framework perspective, this vulnerability maps to CWE-125, which identifies out-of-bounds read conditions as a fundamental memory safety issue. The attack pattern aligns with techniques described in the MITRE ATT&CK framework under the T1499.004 sub-technique for Network Denial of Service, where adversaries leverage software vulnerabilities to disrupt network services. The exploitation requires minimal skill and resources, making it particularly dangerous as it can be automated and deployed at scale against vulnerable systems. Security professionals should note that this vulnerability affects the core scanning functionality of ClamAV, potentially undermining the entire security posture of systems relying on this antivirus solution for threat detection.
Mitigation strategies for CVE-2019-1787 primarily involve immediate software updates to versions 0.101.2 and later, which contain patches addressing the buffer handling deficiencies. Organizations should also implement network segmentation and content filtering to prevent potentially malicious PDF files from reaching vulnerable ClamAV instances. Additional protective measures include monitoring for unusual scanning behavior and implementing intrusion detection systems to identify potential exploitation attempts. Security teams should conduct comprehensive vulnerability assessments to identify all instances of affected ClamAV versions within their infrastructure and prioritize remediation efforts based on risk exposure and criticality of affected systems.