CVE-2008-3244 in scanning engine
Summary
by MITRE
The scanning engine before 4.4.4 in F-Prot Antivirus before 6.0.9.0 allows remote attackers to cause a denial of service (engine crash) via a CHM file with a large nb_dir value that triggers an out-of-bounds read.
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Analysis
by VulDB Data Team • 08/14/2019
The vulnerability identified as CVE-2008-3244 affects the scanning engine component of F-Prot Antivirus software versions prior to 6.0.9.0, specifically targeting versions where the scanning engine is older than 4.4.4. This issue represents a critical security flaw that can be exploited by remote attackers to disrupt the normal operation of the antivirus system. The vulnerability manifests through improper handling of CHM (Compiled HTML Help) files during the scanning process, creating a scenario where legitimate security operations can be compromised.
The technical flaw stems from an insufficient validation mechanism within the CHM file parser of the antivirus scanning engine. When processing a specially crafted CHM file containing an excessively large nb_dir value, the engine fails to properly bounds-check the directory structure information. This leads to an out-of-bounds read condition where the scanning engine attempts to access memory locations beyond the allocated buffer boundaries. The vulnerability is classified as a CWE-129: Improper Validation of Array Index, which falls under the broader category of input validation flaws that can lead to memory corruption issues. The specific nature of the flaw allows attackers to manipulate the directory entry count parameter to trigger memory access violations that ultimately result in application crashes.
The operational impact of this vulnerability extends beyond simple service disruption as it can be leveraged to cause a complete denial of service condition within the antivirus protection framework. Remote attackers can craft malicious CHM files that, when scanned by vulnerable F-Prot versions, will cause the scanning engine to terminate unexpectedly, rendering the antivirus protection ineffective during the period of the crash. This creates a window of vulnerability where the system becomes exposed to other threats that would normally be detected and neutralized by the antivirus software. The attack vector is particularly concerning because CHM files are commonly used in legitimate software installations and documentation, making them an effective delivery mechanism for this type of attack. According to ATT&CK framework, this vulnerability maps to T1499.004: Endpoint Denial of Service, which specifically addresses techniques targeting endpoint systems to prevent normal operation.
Mitigation strategies for this vulnerability require immediate patching of affected F-Prot Antivirus installations to version 6.0.9.0 or later, where the scanning engine has been updated to properly validate CHM file structures. Organizations should implement network segmentation and monitoring to detect unusual scanning patterns that might indicate exploitation attempts. Additionally, security administrators should consider implementing file type restrictions for CHM files in environments where the vulnerability cannot be immediately patched, particularly in critical systems where antivirus availability is essential. The fix implemented by F-Prot developers addresses the root cause by introducing proper bounds checking for the nb_dir parameter during CHM file parsing, preventing the out-of-bounds memory access that previously caused the engine to crash. Regular vulnerability assessments and penetration testing should be conducted to identify similar input validation weaknesses in other security software components, as this type of flaw represents a common pattern in antivirus and security scanning engines.