CVE-2008-1389 in ClamAV
Summary
by MITRE
libclamav/chmunpack.c in the chm-parser in ClamAV before 0.94 allows remote attackers to cause a denial of service (application crash) via a malformed CHM file, related to an "invalid memory access."
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Analysis
by VulDB Data Team • 03/16/2021
The vulnerability identified as CVE-2008-1389 represents a critical denial of service weakness within the ClamAV antivirus software suite, specifically affecting the chm-parser component responsible for processing Compiled HTML Help files. This flaw exists in the libclamav/chmunpack.c module and impacts ClamAV versions prior to 0.94, creating a significant security risk for organizations relying on this popular open-source antivirus solution. The vulnerability stems from inadequate input validation and memory management within the CHM file parsing logic, which fails to properly handle malformed or corrupted CHM archives that could be crafted by malicious actors to exploit the software's parsing routines.
The technical exploitation of this vulnerability occurs through a specific memory access pattern that leads to invalid memory access conditions within the chm-parser's chmunpack.c implementation. When ClamAV attempts to process a specially crafted CHM file containing malformed structures or improper memory references, the parsing routine encounters unexpected data patterns that cause the application to crash or terminate unexpectedly. This invalid memory access condition typically manifests as a segmentation fault or access violation error, resulting in the complete termination of the ClamAV daemon or scanning process. The vulnerability is particularly concerning because CHM files are commonly used in software documentation and help systems, making them a frequent target for attackers seeking to disrupt security scanning operations.
From an operational perspective, this vulnerability creates substantial risk for organizations using ClamAV as part of their security infrastructure, particularly in environments where automated scanning of user-provided files or network traffic is performed. The denial of service impact can be severe, as it effectively disables the antivirus scanning capabilities during the period when the application is crashing and restarting. Attackers could exploit this weakness by delivering malicious CHM files through various attack vectors including email attachments, web downloads, or file sharing systems, potentially causing widespread disruption to security operations. The vulnerability aligns with CWE-125, which describes out-of-bounds read conditions, and represents a classic example of improper input validation leading to memory corruption issues that can be leveraged for denial of service attacks.
Organizations affected by this vulnerability should prioritize immediate remediation through updating to ClamAV version 0.94 or later, which contains the necessary patches to address the memory access validation issues in the chm-parser component. Additionally, network administrators should implement defensive measures including file type filtering for CHM files in high-security environments, implementing additional scanning layers, and monitoring for unusual application crash patterns that might indicate exploitation attempts. The ATT&CK framework categorizes this vulnerability under the T1499.004 technique for network denial of service, as the exploitation directly targets application stability and availability. System administrators should also consider implementing sandboxing techniques for CHM file analysis and establishing robust incident response procedures to quickly identify and contain potential exploitation attempts. The vulnerability demonstrates the importance of proper memory management and input validation in security software, where even seemingly benign file types can become attack vectors when not properly handled by security applications.