CVE-2007-2650 in ClamAV
Summary
by MITRE
The OLE2 parser in Clam AntiVirus (ClamAV) allows remote attackers to cause a denial of service (resource consumption) via an OLE2 file with (1) a large property size or (2) a loop in the FAT file block chain that triggers an infinite loop, as demonstrated via a crafted DOC file.
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Analysis
by VulDB Data Team • 03/15/2021
The vulnerability identified as CVE-2007-2650 represents a critical denial of service flaw within Clam AntiVirus's OLE2 file parsing functionality. This issue affects the core engine responsible for scanning and analyzing Microsoft Office documents, particularly those utilizing the OLE2 (Object Linking and Embedding) container format. The vulnerability stems from inadequate input validation and loop detection mechanisms within the parser implementation, creating exploitable conditions that can be triggered remotely through maliciously crafted Office documents.
The technical flaw manifests in two distinct attack vectors that exploit different aspects of the OLE2 file structure. The first vector involves manipulating property size values within OLE2 files to create excessive memory allocation requests that consume system resources proportional to the malicious input size. The second vector targets the File Allocation Table (FAT) chain processing logic, where crafted files contain circular references that cause the parser to enter infinite loops during block chain traversal operations. Both scenarios result in resource exhaustion that effectively renders the antivirus scanning service unavailable to legitimate users.
This vulnerability directly impacts the operational integrity of ClamAV deployments by enabling remote attackers to consume system resources indefinitely, leading to service disruption and potential system instability. The attack can be executed without requiring authentication or special privileges, making it particularly dangerous in networked environments where antivirus services are continuously processing incoming files. The resource consumption patterns can vary significantly depending on the implementation details of the affected ClamAV version, but all instances demonstrate the potential for complete service unavailability through carefully constructed malicious documents.
The vulnerability aligns with CWE-400, which specifically addresses "Uncontrolled Resource Consumption," and demonstrates characteristics consistent with CWE-835, "Loop with Unreachable Exit Condition." From an operational security perspective, this flaw represents a significant risk to organizations relying on ClamAV for endpoint protection, as it can be exploited to create persistent denial of service conditions that may go undetected until system resources are completely exhausted. The attack vector operates at the application layer, making it particularly challenging to defend against through traditional network-based security controls.
Organizations should implement immediate mitigation strategies including updating to patched versions of ClamAV that contain proper bounds checking and loop detection mechanisms. Network administrators should consider implementing file type filtering to restrict the processing of OLE2-based documents when possible, while also monitoring system resource utilization for unusual patterns that may indicate exploitation attempts. The vulnerability underscores the importance of input validation and resource management in security software, particularly in anti-virus and malware detection systems where processing untrusted input is a fundamental requirement. Additionally, implementing proper timeout mechanisms and resource limits for file processing operations can help prevent exploitation of similar vulnerabilities in other security applications.
The broader implications of this vulnerability extend beyond immediate denial of service conditions to highlight fundamental security considerations in anti-virus engine design. The flaw demonstrates how complex file format parsing logic can introduce unexpected execution paths that lead to resource exhaustion, emphasizing the need for comprehensive testing and validation of parsing algorithms against malicious inputs. Security professionals should also consider implementing sandboxing or virtualization techniques for processing potentially malicious documents, as well as maintaining detailed logging of file processing activities to facilitate detection of exploitation attempts. This vulnerability serves as a reminder of the critical importance of robust input validation and defensive programming practices in security-critical software components.