CVE-2007-6595 in ClamAV
Summary
by MITRE
ClamAV 0.92 allows local users to overwrite arbitrary files via a symlink attack on (1) temporary files used by the cli_gentempfd function in libclamav/others.c or on (2) .ascii files used by sigtool, when utf16-decode is enabled.
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Analysis
by VulDB Data Team • 01/12/2025
The vulnerability identified as CVE-2007-6595 affects ClamAV version 0.92 and represents a significant local privilege escalation risk through symlink attacks targeting temporary file handling mechanisms. This flaw exists within the core file processing functionality of the antivirus software, specifically in how it manages temporary file creation and management during signature processing operations.
The technical implementation of this vulnerability stems from improper handling of temporary file creation in the cli_gentempfd function located in libclamav/others.c. When ClamAV processes certain file types, particularly those involving utf16-decode functionality, it creates temporary files without adequate security measures to prevent symlink attacks. The vulnerability manifests when local users can manipulate the file system to create symbolic links that point to sensitive system files, allowing them to overwrite critical files with arbitrary content. This weakness directly maps to CWE-367, which addresses Time-of-Check to Time-of-Use (TOCTOU) vulnerabilities, where the system checks file permissions or existence at one point and then accesses the file at a later point when the state may have changed.
The operational impact of this vulnerability extends beyond simple file overwriting, as it enables attackers to potentially modify critical system files, configuration data, or even executable components within the ClamAV environment. When utf16-decode functionality is enabled, the vulnerability becomes particularly dangerous as it affects the sigtool utility, which is used for signature management and validation. Attackers could leverage this weakness to inject malicious content into signature files or overwrite system files that ClamAV relies upon for proper operation. The attack vector is particularly insidious because it requires minimal privileges but can result in significant system compromise, making it a prime target for privilege escalation attacks.
The exploitation of this vulnerability aligns with several ATT&CK techniques including T1059 for command execution and T1548 for privilege escalation. The attack requires local system access and leverages the predictable nature of temporary file naming and creation processes within ClamAV. Security professionals should note that this vulnerability demonstrates the critical importance of proper temporary file handling in security software, as antivirus tools often run with elevated privileges and are frequently targeted by attackers seeking to gain system control. Organizations using ClamAV 0.92 should immediately implement mitigations including updating to patched versions, implementing proper file system permissions, and monitoring for suspicious symbolic link creation patterns in temporary directories.
The vulnerability highlights a fundamental security principle that temporary file handling must always consider race conditions and potential symlink attacks. Modern security practices recommend using secure temporary file creation functions that prevent symlink attacks by ensuring files are created with appropriate permissions and that the file creation process is atomic. This vulnerability serves as a reminder that even security tools can contain flaws that attackers can exploit to bypass their protective functions. The issue also underscores the importance of proper input validation and file system access controls, particularly in applications that process untrusted data and operate with elevated privileges. Organizations should conduct comprehensive security reviews of their antivirus implementations and ensure that all temporary file handling follows established secure coding practices to prevent similar vulnerabilities from being introduced in future versions.