CVE-2018-18519 in Best Free Keylogger
Summary
by MITRE
BestXsoftware Best Free Keylogger 5.2.9 allows local users to gain privileges via a Trojan horse "%PROGRAMFILES%\BFK 5.2.9\syscrb.exe" file because of insecure permissions for the BUILTIN\Users group.
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Analysis
by VulDB Data Team • 04/14/2020
This vulnerability exists in BestXsoftware Best Free Keylogger version 5.2.9, representing a critical privilege escalation flaw that affects local system security. The vulnerability stems from improper file permissions assigned to the syscrb.exe executable located in the program files directory. Specifically, the BUILTIN\Users group has been granted write permissions to this critical system file, creating a dangerous trojan horse attack vector. This misconfiguration allows any local user to replace or modify the legitimate syscrb.exe binary with malicious code, effectively bypassing standard security controls. The vulnerability demonstrates poor software development practices and inadequate security hardening of installed applications.
The technical implementation of this flaw involves the Windows file permission model where the syscrb.exe file lacks proper access control restrictions. When the BUILTIN\Users group possesses write permissions to a system-critical executable within the program files directory, it creates an opportunity for privilege escalation attacks. Attackers can simply replace the legitimate executable with a malicious version that executes with elevated privileges, potentially gaining system-level access. This issue directly relates to CWE-276, which addresses incorrect permissions for critical resources, and represents a classic example of insecure file permissions in Windows environments. The vulnerability is particularly dangerous because it operates at the local system level without requiring network connectivity or complex exploitation techniques.
The operational impact of this vulnerability extends beyond simple privilege escalation to encompass broader security implications for enterprise environments. Local users who can exploit this flaw can effectively compromise entire systems by executing malicious code with elevated privileges, potentially leading to data theft, system corruption, or further lateral movement within networks. The vulnerability affects organizations that have deployed this keylogger software, as it creates a persistent backdoor mechanism that can be exploited by both malicious insiders and external attackers who gain local access. This represents a significant risk to organizations following the principle of least privilege, as it undermines the fundamental security assumptions of user access controls. The attack vector aligns with ATT&CK technique T1068, which covers privilege escalation through local exploitation of system vulnerabilities.
Organizations should implement immediate remediation measures including verifying and correcting file permissions for all installed software, particularly executables within program files directories. The recommended mitigation involves removing write permissions for the BUILTIN\Users group on the syscrb.exe file and ensuring that only authorized administrators possess modification rights. Additionally, system administrators should conduct comprehensive audits of installed applications to identify similar permission misconfigurations. Regular security assessments should include verification of file permissions and access control lists to prevent such vulnerabilities from being introduced through software installation processes. The remediation process should also involve updating to newer versions of the software if available, as this vulnerability may have been addressed in subsequent releases. System monitoring should be enhanced to detect unauthorized modifications to critical system files, and security policies should be updated to prevent installation of software with insecure default configurations.