CVE-2018-15378 in ClamAV
Summary
by MITRE
A vulnerability in ClamAV versions prior to 0.100.2 could allow an attacker to cause a denial of service (DoS) condition. The vulnerability is due to an error related to the MEW unpacker within the "unmew11()" function (libclamav/mew.c), which can be exploited to trigger an invalid read memory access via a specially crafted EXE file.
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Analysis
by VulDB Data Team • 03/15/2025
The vulnerability identified as CVE-2018-15378 represents a critical denial of service weakness in ClamAV antivirus software affecting versions prior to 0.100.2. This flaw resides within the MEW unpacker functionality specifically within the unmew11() function located in the libclamav/mew.c source file. The issue manifests when ClamAV processes specially crafted executable files that exploit memory access patterns leading to invalid read operations. The vulnerability stems from inadequate input validation and memory management within the decompression routines that handle MEW (Microsoft Enhanced Windows) format files. Attackers can leverage this weakness by constructing malicious executable files that, when scanned by vulnerable ClamAV instances, trigger the flawed memory access pattern. The root cause aligns with CWE-125, which describes out-of-bounds read vulnerabilities, and CWE-787, which covers out-of-bounds write conditions. This vulnerability directly impacts the availability and reliability of antivirus scanning services, as successful exploitation causes the ClamAV daemon to crash or become unresponsive.
The operational impact of CVE-2018-15378 extends beyond simple service disruption to potentially compromise enterprise security infrastructure. Organizations relying on ClamAV for email filtering, file scanning, or endpoint protection face significant risks when systems run vulnerable versions. The DoS condition can be triggered through various attack vectors including email attachments, file downloads, or network traffic analysis. From an attacker perspective, this vulnerability maps to ATT&CK technique T1499.004, which involves network denial of service attacks, and T1566.001, covering spearphishing attachments. The vulnerability is particularly concerning in enterprise environments where ClamAV serves as a critical security control, as it can be exploited to disrupt security operations and potentially mask other malicious activities. Network administrators and security teams must consider the cascading effects of such a vulnerability, as it could be used to disable security scanning capabilities across multiple systems simultaneously.
Mitigation strategies for CVE-2018-15378 focus primarily on immediate version upgrades to ClamAV 0.100.2 or later releases where the vulnerability has been patched. System administrators should implement comprehensive patch management procedures to ensure all ClamAV instances across the network are updated promptly. Additional defensive measures include implementing network segmentation to limit the impact of potential exploitation, deploying intrusion detection systems to monitor for suspicious file scanning patterns, and establishing robust backup and recovery procedures for antivirus infrastructure. Security teams should also consider implementing file reputation systems and behavioral analysis to detect and block malicious files before they reach the ClamAV scanning layer. The patch addresses the underlying memory management error in the unmew11() function through proper bounds checking and input validation, preventing the invalid read conditions that previously led to system crashes. Organizations should conduct thorough testing of updated ClamAV versions in controlled environments before widespread deployment to ensure compatibility with existing security policies and scanning configurations.