CVE-2017-6418 in ClamAV
Summary
by MITRE
libclamav/message.c in ClamAV 0.99.2 allows remote attackers to cause a denial of service (out-of-bounds read) via a crafted e-mail message.
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Analysis
by VulDB Data Team • 12/15/2022
The vulnerability identified as CVE-2017-6418 represents a critical out-of-bounds read flaw within the ClamAV email scanning functionality. This issue exists in the message.c file of ClamAV version 0.99.2, where the software fails to properly validate input data from email messages before processing them. The flaw specifically manifests when ClamAV encounters specially crafted email content that triggers an invalid memory access pattern during the parsing of message headers or content. Such vulnerabilities are particularly dangerous in email security systems since they can be exploited by malicious actors to disrupt services without requiring authentication or elevated privileges.
The technical nature of this vulnerability places it squarely within the CWE-125 category of out-of-bounds read conditions, which is a common class of memory safety issues that can lead to system instability and potential exploitation. When ClamAV processes the malformed email message, the software attempts to read memory locations beyond the allocated buffer boundaries, causing the application to crash or behave unpredictably. This behavior directly maps to the ATT&CK technique T1499.004 for Network Denial of Service, where adversaries can leverage software flaws to disrupt system availability. The out-of-bounds read occurs during the message parsing phase, indicating that the input validation mechanisms are insufficient to handle malformed email structures that exceed expected parameter limits.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise the integrity of email security infrastructure. Organizations relying on ClamAV for email filtering may experience unexpected service interruptions when processing legitimate emails that contain the crafted malicious content, leading to potential security gaps in their email protection. The remote exploitation capability means that attackers can trigger this vulnerability from outside the network, making it particularly dangerous for email servers that process messages from untrusted sources. This type of denial of service attack can be used to overwhelm systems with repeated requests or to create service interruptions that allow other attacks to proceed without detection.
Mitigation strategies for CVE-2017-6418 should prioritize immediate software updates to versions that have patched the memory validation issue in the message.c file. Organizations should implement network segmentation and email filtering rules that can identify and quarantine suspicious email patterns before they reach the ClamAV scanning layer. Additionally, monitoring systems should be enhanced to detect unusual service disruptions or memory access patterns that could indicate exploitation attempts. The vulnerability highlights the importance of robust input validation in security software and demonstrates why regular security updates and thorough testing of security tooling are essential components of any cybersecurity program. Security teams should also consider implementing redundant email scanning solutions to maintain protection levels even when individual components are under attack.