CVE-2008-5050 in ClamAV
Summary
by MITRE
Off-by-one error in the get_unicode_name function (libclamav/vba_extract.c) in Clam Anti-Virus (ClamAV) before 0.94.1 allows remote attackers to cause a denial of service (crash) or possibly execute arbitrary code via a crafted VBA project file, which triggers a heap-based buffer overflow.
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Analysis
by VulDB Data Team • 03/16/2021
The vulnerability identified as CVE-2008-5050 represents a critical security flaw within ClamAV's handling of Microsoft Office VBA project files, specifically within the get_unicode_name function located in libclamav/vba_extract.c. This issue affects ClamAV versions prior to 0.94.1 and demonstrates a classic off-by-one error that fundamentally compromises the software's memory management integrity. The flaw occurs when processing malformed VBA project files that contain specially crafted unicode sequences, creating a condition where the application fails to properly validate buffer boundaries during string extraction operations.
The technical implementation of this vulnerability stems from improper bounds checking within the get_unicode_name function, which processes unicode character sequences from VBA project files. When a maliciously constructed VBA file is processed, the function calculates buffer sizes incorrectly due to the off-by-one error, resulting in a heap-based buffer overflow condition. This memory corruption occurs because the application allocates insufficient memory space for the extracted unicode string, allowing subsequent write operations to overwrite adjacent memory regions. The vulnerability's classification as heap-based indicates that the overflow affects dynamically allocated memory segments, potentially leading to unpredictable behavior including application crashes or memory corruption that could be exploited for code execution.
The operational impact of this vulnerability extends beyond simple denial of service to encompass potential remote code execution capabilities, making it particularly dangerous in enterprise environments where email scanning and file validation are critical security functions. When a compromised VBA file is processed by an affected ClamAV instance, the application may crash and terminate unexpectedly, causing service disruption and potential data loss. However, the more severe implications arise from the possibility of arbitrary code execution, which could allow attackers to execute malicious payloads within the context of the scanning process. This represents a significant escalation from basic denial of service, as it could enable attackers to compromise the entire security infrastructure that relies on ClamAV for malware detection.
The vulnerability aligns with CWE-121, heap-based buffer overflow, and demonstrates characteristics consistent with ATT&CK technique T1059.007 for command and scripting interpreter execution, as successful exploitation could enable attackers to execute arbitrary code on systems running vulnerable ClamAV versions. Organizations deploying ClamAV for email filtering, file scanning, or endpoint protection are particularly at risk, as the vulnerability can be triggered through routine file processing without requiring user interaction. The attack vector is primarily remote, as attackers can deliver malicious VBA files through email attachments or file sharing systems, making this a particularly concerning threat for organizations that do not maintain up-to-date security patches. Security professionals should prioritize patching affected systems to prevent exploitation, as the vulnerability represents a significant risk to network security infrastructure that relies on proper malware detection capabilities.
Mitigation strategies should focus on immediate patch deployment to ClamAV versions 0.94.1 and later, which contain the necessary fixes for the buffer overflow condition. System administrators should implement comprehensive patch management procedures to ensure all instances of ClamAV across the organization are updated promptly. Additional protective measures include implementing network-based intrusion detection systems that can identify and block known malicious VBA file patterns, as well as establishing strict file validation policies that limit the processing of potentially malicious office documents. Organizations should also consider implementing sandboxing techniques for suspicious file analysis and maintaining regular security audits to verify that all ClamAV instances are properly patched and configured according to security best practices.