CVE-2018-0202 in ClamAV
Summary
by MITRE
clamscan in ClamAV before 0.99.4 contains a vulnerability that could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. The vulnerability is due to improper input validation checking mechanisms when handling Portable Document Format (.pdf) files sent to an affected device. An unauthenticated, remote attacker could exploit this vulnerability by sending a crafted .pdf file to an affected device. This action could cause an out-of-bounds read when ClamAV scans the malicious file, allowing the attacker to cause a DoS condition. This concerns pdf_parse_array and pdf_parse_string in libclamav/pdfng.c. Cisco Bug IDs: CSCvh91380, CSCvh91400.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 02/24/2023
The vulnerability identified as CVE-2018-0202 affects ClamAV's clamscan utility version 0.99.3 and earlier, presenting a critical denial of service risk that can be exploited remotely without authentication. This weakness stems from inadequate input validation mechanisms within the PDF processing components of ClamAV's libclamav library, specifically in the pdfng.c module where the pdf_parse_array and pdf_parse_string functions handle document parsing operations. The flaw represents a classic buffer over-read condition that occurs when processing malformed PDF files, creating a scenario where legitimate scanning operations can be disrupted by maliciously crafted documents. This vulnerability directly impacts organizations that rely on ClamAV for malware detection and file scanning, particularly in environments where PDF files are frequently processed or where automated scanning systems are deployed.
The technical exploitation of this vulnerability occurs when ClamAV encounters specially crafted PDF files that contain malformed data structures within array or string parsing operations. The improper validation allows an attacker to manipulate the parsing functions in such a way that memory access occurs beyond the bounds of allocated buffers, leading to unpredictable behavior and ultimately system instability. This out-of-bounds read condition manifests as a crash or hang within the scanning process, effectively causing a denial of service that prevents legitimate file scanning operations from completing successfully. The vulnerability's remote nature means that attackers can trigger the condition from outside the target network without requiring any authentication credentials, making it particularly dangerous for systems that process untrusted PDF content automatically.
From an operational perspective, this vulnerability creates significant risks for organizations that depend on ClamAV for security scanning, especially in email gateways, file servers, and endpoint protection systems where PDF files are commonly encountered. The denial of service condition can result in complete scanning system failures, potentially leaving networks vulnerable to other threats while the scanning service remains unavailable. The impact extends beyond simple service disruption as it can affect automated security workflows, create false positives in security monitoring, and potentially provide attackers with information about system vulnerabilities through service availability patterns. Organizations using ClamAV in production environments face the risk of extended downtime and degraded security posture when this vulnerability is exploited.
The remediation for CVE-2018-0202 requires immediate deployment of ClamAV version 0.99.4 or later, which includes patched implementations of the pdfng.c module functions that properly validate input data before processing. Organizations should also implement network segmentation and access controls to limit exposure of systems running ClamAV to untrusted PDF content, while monitoring for potential exploitation attempts through unusual scanning patterns or service disruptions. Security teams should conduct thorough vulnerability assessments to identify all systems running affected ClamAV versions and ensure proper patch management procedures are in place to prevent similar issues in the future. This vulnerability aligns with CWE-129, which addresses improper validation of input boundaries, and represents a typical example of how buffer over-read conditions can be exploited to achieve denial of service in security scanning applications. The ATT&CK framework categorizes this as a privilege escalation technique through service disruption, where adversaries leverage software vulnerabilities to compromise system availability and maintain persistent access through continued exploitation attempts.