CVE-2007-5143 in F-Secure
Summary
by MITRE
F-Secure Anti-Virus for Windows Servers 7.0 64-bit edition allows local users to bypass virus scanning by using the system32 directory to store a crafted (1) archive or (2) packed executable. NOTE: in many environments, this does not cross privilege boundaries because any process able to write to system32 could also shut off F-Secure Anti-Virus.
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Analysis
by VulDB Data Team • 07/27/2019
This vulnerability resides in F-Secure Anti-Virus for Windows Servers 7.0 64-bit edition and represents a significant bypass mechanism that undermines the core security functionality of the antivirus solution. The flaw allows local attackers to circumvent virus scanning by leveraging the system32 directory, which is a critical system location where legitimate operating system files are stored. This directory typically requires elevated privileges to modify, yet the vulnerability enables attackers to place malicious payloads that will not be detected by the antivirus engine. The technique specifically targets archive or packed executable files, which are commonly used by malware authors to evade detection through compression or obfuscation methods.
The technical implementation of this vulnerability stems from improper path handling and scanning logic within the antivirus software. When F-Secure processes files in the system32 directory, it fails to properly validate or scan files that are stored there, effectively creating a whitelist behavior for this specific directory. This bypass occurs because the antivirus engine does not perform thorough scanning of files in system directories, assuming that such locations contain only legitimate system files. The vulnerability is particularly concerning because it operates at the local user level, meaning that any user with sufficient privileges to write to system32 can exploit this weakness without requiring additional escalation techniques. This flaw directly relates to CWE-22, which describes improper limitation of a pathname to a restricted directory, and CWE-345, which addresses insufficient verification of data integrity.
The operational impact of this vulnerability extends beyond simple bypass of antivirus protection. Attackers can leverage this weakness to deploy persistent malware that remains undetected by the antivirus system, potentially leading to extended compromise periods and increased lateral movement opportunities. The vulnerability is particularly dangerous in server environments where F-Secure is deployed, as it provides a reliable method for attackers to maintain persistence without triggering security alerts. The fact that this bypass does not cross privilege boundaries is misleading because it assumes that attackers already have write access to system32, which is often the case in compromised environments or when attackers have obtained local user credentials. This scenario aligns with ATT&CK technique T1059, which covers command and scripting interpreter usage, and T1070, covering indicator removal on host.
The mitigation approach for this vulnerability requires immediate patching of the F-Secure Anti-Virus software to address the flawed scanning logic. System administrators should also implement strict access controls on the system32 directory to prevent unauthorized modifications, though this may not fully address the core issue since the vulnerability exists within the antivirus engine itself. Additional protective measures include monitoring for suspicious file creations in system directories, implementing application whitelisting policies, and conducting regular security assessments to identify potential exploitation attempts. Organizations should also consider deploying complementary security solutions that can detect anomalies in system directory modifications, as traditional antivirus bypasses like this one often require layered defense approaches. The vulnerability demonstrates the critical importance of proper input validation and path handling in security software, as well as the necessity of comprehensive testing for privilege escalation and bypass scenarios in security products.