CVE-2005-3318 in CHM lib
Summary
by MITRE
Buffer overflow in the _chm_decompress_block function in CHM lib (chmlib) before 0.37, as used in products such as KchmViewer, allows attackers execute arbitrary code, a different vulnerability than CVE-2005-2930.
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Analysis
by VulDB Data Team • 06/12/2019
The vulnerability identified as CVE-2005-3318 represents a critical buffer overflow flaw within the chmlib library, specifically within the _chm_decompress_block function. This library serves as a core component for handling compressed help files in the CHM format, which is widely utilized across various software applications and operating systems. The vulnerability affects versions prior to 0.37 of chmlib and has been particularly impactful in products such as KchmViewer, which rely on this library for processing CHM files. The flaw stems from inadequate bounds checking during the decompression process, where the function fails to properly validate input data lengths before writing to allocated memory buffers.
The technical implementation of this vulnerability occurs when the _chm_decompress_block function processes compressed data streams without sufficient validation of the decompressed data size against the allocated buffer space. This allows an attacker to craft malicious CHM files containing specially formatted compressed blocks that exceed the intended buffer boundaries during decompression operations. When the vulnerable library processes such crafted input, the overflow can overwrite adjacent memory locations, potentially corrupting program execution flow and enabling arbitrary code execution. The vulnerability operates at the binary level within the decompression algorithm, making it particularly dangerous as it can be triggered simply by opening a malicious CHM file, requiring no additional user interaction beyond the standard file opening process.
From an operational perspective, this vulnerability presents a significant risk to systems running affected software, as it enables remote code execution through malicious CHM files. The impact extends beyond individual applications to potentially compromise entire systems, especially when the vulnerable libraries are used in web browsers, email clients, or other applications that handle CHM files from untrusted sources. Attackers can exploit this vulnerability by embedding malicious content within CHM archives, which can then be delivered through various attack vectors including phishing emails, compromised websites, or malicious file sharing platforms. The vulnerability is particularly concerning because CHM files are commonly used in software documentation, help systems, and educational materials, making them frequent targets for social engineering attacks.
The security implications of CVE-2005-3318 align with CWE-121, which addresses stack-based buffer overflow conditions, and can be categorized under ATT&CK technique T1059.007 for command and scripting interpreter usage. The vulnerability demonstrates how legacy library components can harbor critical security flaws that persist across multiple product implementations, highlighting the importance of regular security updates and dependency management. Organizations should prioritize patching affected systems and implementing network segmentation controls to limit potential exploitation. Mitigation strategies include updating to chmlib version 0.37 or later, implementing file type validation for CHM files, and employing sandboxing techniques when processing untrusted CHM content. Additionally, security monitoring should include detection of suspicious CHM file access patterns and network traffic containing CHM content from unusual sources. The vulnerability serves as a reminder of the critical importance of maintaining up-to-date third-party libraries and the potential for seemingly benign file format processing to become attack vectors for sophisticated exploitation techniques.