CVE-2005-3500 in ClamAV
Summary
by MITRE
The tnef_attachment function in tnef.c for Clam AntiVirus (ClamAV) before 0.87.1 allows remote attackers to cause a denial of service (infinite loop and memory exhaustion) via a crafted value in a CAB file that causes ClamAV to repeatedly scan the same block.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 07/21/2024
The vulnerability identified as CVE-2005-3500 represents a critical denial of service flaw within Clam AntiVirus version 0.87.1 and earlier, specifically affecting the tnef_attachment function in the tnef.c component. This weakness stems from improper handling of crafted values within CAB files, which are commonly used for compressed data storage and distribution. The vulnerability manifests when ClamAV processes specially constructed CAB file contents that contain malformed TNEF (Transport Neutral Encapsulation Format) attachments, leading to a condition where the software enters an infinite loop while scanning the same data block repeatedly.
The technical exploitation of this vulnerability occurs through the manipulation of CAB file structures that contain embedded TNEF data with crafted parameters. When ClamAV's tnef_attachment function encounters such malformed data, it fails to properly validate the input parameters and instead follows a recursive scanning pattern that repeatedly processes identical data blocks. This flaw directly maps to CWE-835, which addresses the issue of infinite loops in software systems, where a loop lacks proper termination conditions or fails to update loop control variables correctly. The vulnerability demonstrates a classic case of insufficient input validation and inadequate boundary checking within the decompression and scanning logic of the antivirus engine.
The operational impact of this vulnerability is severe and can be exploited by remote attackers to disrupt the availability of ClamAV services. An attacker can craft a malicious CAB file containing the specially designed TNEF attachment that triggers the infinite loop behavior, causing the antivirus scanner to consume excessive system resources including CPU cycles and memory allocation. This resource exhaustion can lead to complete system unresponsiveness or service disruption, particularly in environments where ClamAV is deployed as a critical security component for email filtering or file scanning. The vulnerability affects systems where ClamAV processes untrusted file content, making it particularly dangerous in network security appliances, email servers, and endpoint protection systems that rely on ClamAV for malware detection.
The mitigation strategy for CVE-2005-3500 involves immediate patching of ClamAV installations to version 0.87.1 or later, where the vulnerability has been addressed through improved input validation and loop termination conditions in the tnef_attachment function. Organizations should implement comprehensive patch management procedures to ensure all ClamAV instances are updated promptly. Additionally, network administrators should consider implementing additional layers of protection such as file type filtering, size limitations on incoming files, and sandboxing techniques for suspicious file processing. From an ATT&CK framework perspective, this vulnerability aligns with technique T1499.004, which covers network denial of service attacks through resource exhaustion, and T1566.001, which involves spearphishing with attachments that could contain the malicious CAB files designed to exploit this flaw. The remediation process should also include monitoring for unusual resource consumption patterns that might indicate exploitation attempts and implementing proper logging to track file processing activities that could trigger the vulnerable code path.