CVE-2011-1003 in ClamAV
Summary
by MITRE
Double free vulnerability in the vba_read_project_strings function in vba_extract.c in libclamav in ClamAV before 0.97 might allow remote attackers to execute arbitrary code via crafted Visual Basic for Applications (VBA) data in a Microsoft Office document. NOTE: some of these details are obtained from third party information.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 01/16/2025
The CVE-2011-1003 vulnerability represents a critical double free memory corruption issue within ClamAV's libclamav library, specifically in the vba_read_project_strings function located in vba_extract.c. This vulnerability arises from improper memory management practices where the same memory block is freed twice during the processing of Visual Basic for Applications data within Microsoft Office documents. The flaw occurs when ClamAV attempts to parse maliciously crafted VBA macros, creating conditions where memory deallocation operations are executed redundantly, leading to unpredictable memory state corruption that can be exploited by remote attackers.
The technical implementation of this vulnerability stems from a classic memory safety issue that maps to CWE-415, which describes double free conditions in software systems. When ClamAV processes Office documents containing malformed VBA data, the vba_read_project_strings function fails to properly track memory allocations and deallocations, resulting in a scenario where a memory pointer is passed to the free() function twice. This creates a heap corruption condition that can be leveraged by attackers to manipulate program execution flow and potentially execute arbitrary code with the privileges of the ClamAV process. The vulnerability is particularly dangerous because it operates during document scanning operations, making it exploitable through typical email security or file validation workflows.
The operational impact of CVE-2011-1003 extends beyond simple code execution, as it can be weaponized in various attack scenarios within the ATT&CK framework under the T1059.005 technique for command and control through office applications. Attackers can craft malicious Office documents containing specially designed VBA macros that trigger the double free condition when scanned by vulnerable ClamAV installations. This vulnerability affects organizations using ClamAV versions prior to 0.97 in email security gateways, network file scanning systems, and endpoint protection solutions. The remote execution capability means that simply opening or scanning a malicious document can result in system compromise, making this vulnerability particularly attractive to threat actors targeting enterprise security infrastructure.
Organizations should prioritize immediate patching of ClamAV installations to version 0.97 or later, which contains the necessary memory management fixes to prevent the double free condition. Additionally, network administrators should implement multiple layers of defense including email filtering rules that block suspicious Office documents, network segmentation to limit the impact of potential compromises, and regular security assessments of email security infrastructure. The vulnerability highlights the importance of proper memory management in security software and demonstrates why regular security updates and vulnerability assessments are critical for maintaining secure infrastructure. Organizations should also consider implementing additional monitoring for unusual memory allocation patterns or system behavior that could indicate exploitation attempts, as the heap corruption effects may not always result in immediate code execution but could enable more sophisticated attack vectors.