CVE-2019-1786 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 0.101.0 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 an 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-2019-1786 resides within the Portable Document Format scanning capabilities of Clam AntiVirus software, specifically affecting versions 0.101.0 and 0.101.1. This security flaw represents a critical weakness in the software's ability to process PDF files safely, creating a potential entry point for malicious actors seeking to disrupt system operations. The vulnerability manifests through insufficient input validation and buffer management mechanisms that are essential for processing file data during antivirus scanning operations. The affected ClamAV versions demonstrate a failure in implementing proper bounds checking during PDF file parsing, particularly when handling the indexing of remaining file data within memory buffers.
The technical exploitation of this vulnerability occurs through crafted PDF files that trigger an out-of-bounds read condition within the ClamAV scanning engine. This specific flaw stems from inadequate data handling mechanisms that fail to properly validate buffer boundaries when processing PDF content, particularly during the indexing phase of file analysis. When an attacker submits maliciously constructed PDF documents to a system running the vulnerable ClamAV software, the scanning process attempts to read data beyond allocated memory boundaries, causing the application to crash and resulting in a denial of service condition. The vulnerability operates at the memory management level, where the software fails to properly account for buffer limits during PDF file processing operations, creating an exploitable condition that can be remotely triggered without authentication requirements.
The operational impact of CVE-2019-1786 extends beyond simple service disruption, potentially affecting organizations that rely heavily on ClamAV for email filtering, file scanning, and endpoint protection. Systems running vulnerable versions of ClamAV could experience complete service interruption when processing legitimate PDF files, as the software crashes and becomes unresponsive to further scanning operations. This vulnerability particularly affects email servers, network security appliances, and endpoint protection systems that utilize ClamAV for PDF content inspection. The remote exploitation capability means that attackers can trigger this condition from external networks without requiring local access or authentication credentials, making it a significant concern for organizations with exposed scanning services. The DoS condition can persist until the affected system is manually restarted or the ClamAV service is manually restarted, potentially creating extended downtime for critical security infrastructure.
Organizations should immediately upgrade to ClamAV versions that have addressed this vulnerability, typically those released after the patching timeline for CVE-2019-1786. The mitigation strategy involves implementing proper input validation and buffer boundary checking mechanisms within the PDF processing pipeline, which aligns with common security practices outlined in industry standards such as CWE-129 for improper validation of array index and CWE-131 for incorrect calculation of buffer size. Network administrators should also consider implementing additional protective measures such as PDF file content filtering, network segmentation, and monitoring for suspicious file upload activities. The vulnerability demonstrates the importance of proper buffer management and input validation in security software, as highlighted by ATT&CK technique T1499.004 for Network Denial of Service, where the exploitation creates a condition that renders network services unavailable to legitimate users. This vulnerability underscores the necessity for security software vendors to implement comprehensive testing and validation procedures for file format processing capabilities, particularly for widely used formats like PDF that are commonly targeted in security attacks.