CVE-2007-1997 in ClamAV
Summary
by MITRE
Integer signedness error in the (1) cab_unstore and (2) cab_extract functions in libclamav/cab.c in Clam AntiVirus (ClamAV) before 0.90.2 allow remote attackers to execute arbitrary code via a crafted CHM file that contains a negative integer, which passes a signed comparison and leads to a stack-based buffer overflow.
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Analysis
by VulDB Data Team • 07/14/2021
The vulnerability described in CVE-2007-1997 represents a critical integer signedness error within the ClamAV antivirus software library that affects the handling of CHM (Compiled HTML Help) files. This flaw exists in the cab_unstore and cab_extract functions located in the libclamav/cab.c file of ClamAV versions prior to 0.90.2. The issue stems from improper handling of integer values during file decompression operations, creating a condition where negative integers can be processed in contexts that expect positive values.
The technical implementation of this vulnerability involves a stack-based buffer overflow that occurs when maliciously crafted CHM files are processed by the affected ClamAV versions. When the cab_unstore and cab_extract functions encounter negative integer values in the CHM file structure, these values bypass signed comparison checks that should prevent invalid memory operations. The flaw specifically manifests when the integer values representing file offsets or sizes are treated as unsigned quantities while being compared against signed thresholds, allowing attackers to manipulate the control flow of the decompression routines.
The operational impact of this vulnerability is severe as it enables remote code execution attacks against systems running vulnerable ClamAV versions. Attackers can craft malicious CHM files that contain negative integers in their internal structures, causing the vulnerable software to allocate insufficient buffer space or access memory locations outside the intended boundaries. This allows attackers to overwrite adjacent memory locations with malicious code, potentially leading to complete system compromise. The vulnerability is particularly dangerous in environments where ClamAV is used for automatic file scanning, such as email servers, web gateways, or file sharing systems.
This vulnerability aligns with CWE-190, which describes integer overflow and underflow conditions, and specifically relates to CWE-129, which covers insufficient validation of array indices. The attack pattern follows techniques described in the MITRE ATT&CK framework under T1059 for command and scripting interpreter and T1203 for exploitation for privilege escalation. The vulnerability demonstrates how improper input validation and integer handling can create critical security flaws in antivirus software that processes untrusted file formats. Organizations should prioritize updating to ClamAV 0.90.2 or later versions that contain patches addressing this signedness error, while also implementing network segmentation and file validation policies to reduce attack surface exposure.