CVE-2007-0897 in ClamAV
Summary
by MITRE
Clam AntiVirus ClamAV before 0.90 does not close open file descriptors under certain conditions, which allows remote attackers to cause a denial of service (file descriptor consumption and failed scans) via CAB archives with a cabinet header record length of zero, which causes a function to return without closing a file descriptor.
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Analysis
by VulDB Data Team • 07/13/2021
The vulnerability identified as CVE-2007-0897 affects Clam AntiVirus ClamAV versions prior to 0.90, representing a significant denial of service weakness that stems from improper file descriptor management within the application's handling of CAB archive files. This flaw manifests when ClamAV processes CAB archives containing a cabinet header record with a length of zero, creating a condition where the system fails to properly close file descriptors that were opened during the scanning process. The issue resides in the application's resource management logic, where specific error conditions prevent the cleanup of open file handles, leading to progressive resource exhaustion over time.
The technical implementation of this vulnerability involves the improper closure of file descriptors during the parsing of CAB archive structures, specifically when encountering malformed header records with zero length fields. When ClamAV encounters such a record, the processing function returns early without executing the necessary file descriptor closing operations, resulting in a resource leak that accumulates with each subsequent scan attempt. This behavior directly violates proper resource management practices and creates a predictable pattern of resource consumption that remote attackers can exploit systematically. The flaw operates at the application layer, specifically within the archive parsing subsystem, and represents a classic case of resource leak vulnerability that can be categorized under CWE-404, which deals with improper resource management.
The operational impact of this vulnerability extends beyond simple service disruption to create a persistent denial of service condition that can severely degrade system performance and availability. As the file descriptor leak accumulates, the system gradually consumes available file handles, eventually reaching the maximum limit imposed by the operating system. This prevents ClamAV from performing subsequent scans and can potentially cause the entire antivirus service to become unresponsive or crash entirely. Attackers can exploit this weakness by simply submitting CAB files with zero-length header records, requiring minimal effort to cause significant disruption to systems relying on ClamAV for malware detection and prevention. The vulnerability affects systems running vulnerable versions of ClamAV and can be particularly problematic in environments where continuous scanning is required, as the resource exhaustion occurs incrementally and may not be immediately apparent to administrators.
Mitigation strategies for CVE-2007-0897 primarily involve upgrading to ClamAV version 0.90 or later, which includes the necessary code fixes to properly close file descriptors regardless of error conditions during CAB archive processing. Organizations should implement regular patch management procedures to ensure all systems running ClamAV are updated with the latest security patches. Additionally, system administrators can monitor file descriptor usage on systems running ClamAV to detect potential resource exhaustion patterns before they lead to complete service disruption. Network-level controls can be implemented to filter or quarantine suspicious CAB files before they reach the antivirus scanning system, reducing the attack surface. From a defensive perspective, this vulnerability aligns with ATT&CK technique T1499.004, which involves resource exhaustion attacks targeting availability through file descriptor consumption, making it a valuable target for security teams to address through both preventive and detective controls. The fix implemented in ClamAV 0.90 demonstrates proper error handling and resource management practices that should serve as a reference for similar applications processing archive files or other structured data formats.