CVE-2005-2920 in ClamAV
Summary
by MITRE
Buffer overflow in libclamav/upx.c in Clam AntiVirus (ClamAV) before 0.87 allows remote attackers to execute arbitrary code via a crafted UPX packed executable.
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Analysis
by VulDB Data Team • 11/22/2024
The vulnerability identified as CVE-2005-2920 represents a critical buffer overflow flaw within the Clam AntiVirus software suite, specifically affecting the libclamav/upx.c component. This issue exists in ClamAV versions prior to 0.87 and creates a significant security risk that can be exploited remotely by malicious actors. The vulnerability manifests when the software processes executable files that have been packed using the UPX (Ultimate Packer for eXecutables) compression utility, which is commonly used to reduce file sizes and obfuscate malware. The buffer overflow occurs during the decompression and analysis phase of UPX-packed executables, where insufficient bounds checking allows an attacker to overflow memory buffers and potentially execute arbitrary code on the target system.
The technical implementation of this vulnerability stems from inadequate input validation within the UPX unpacking routine. When ClamAV encounters a UPX-packed executable, it attempts to decompress and analyze the file structure to detect potential threats. The flaw occurs in the handling of compressed data headers and metadata where the software fails to properly validate the size parameters of the decompressed content. This lack of proper bounds checking enables attackers to craft specially designed UPX-packed executables that contain malicious data structures exceeding the allocated buffer space. The overflow can overwrite adjacent memory locations including return addresses and function pointers, which allows for code execution control. This type of vulnerability is classified as a classic stack-based buffer overflow and aligns with CWE-121, which describes the condition where a program writes to a buffer beyond the boundaries of that buffer, leading to memory corruption and potential code execution.
The operational impact of this vulnerability extends beyond simple remote code execution, as it affects the core functionality of anti-virus protection systems. Attackers can leverage this flaw to bypass security measures by uploading or transmitting malicious UPX-packed files that will be processed by vulnerable ClamAV installations. This creates a dangerous scenario where the very software designed to protect systems becomes the vector for compromise. The vulnerability is particularly concerning in networked environments where ClamAV might be processing files from untrusted sources such as email attachments, file downloads, or network shares. Organizations using affected versions of ClamAV face significant risk of unauthorized system access, data exfiltration, and potential lateral movement within their networks. The attack surface is broadened by the common usage of UPX packing, which makes this vulnerability exploitable across various threat vectors including phishing campaigns, malicious software distribution, and targeted attacks against security-conscious organizations.
Mitigation strategies for CVE-2005-2920 require immediate patching of ClamAV installations to versions 0.87 or later where the buffer overflow has been addressed. Organizations should implement comprehensive network monitoring to detect potential exploitation attempts and establish robust patch management procedures to ensure all systems remain up-to-date. Security teams should also consider implementing additional layers of protection including network segmentation, file integrity monitoring, and behavioral analysis to detect anomalous file processing activities. The vulnerability demonstrates the importance of proper input validation and memory management in security software, as the flaw exists within a component that processes potentially malicious content. This aligns with ATT&CK technique T1059.007 for command and scripting interpreter, where attackers might leverage such vulnerabilities to execute malicious code through legitimate system processes. Organizations should also conduct regular security assessments of their anti-virus configurations and ensure that threat detection capabilities are not compromised by vulnerabilities in the protection software itself, as this vulnerability could potentially allow attackers to disable or bypass security controls entirely.