CVE-2018-7535 in TotalAV
Summary
by MITRE
An issue was discovered in TotalAV v4.1.7. An unprivileged user could modify or overwrite all of the product's files because of weak permissions (Everyone:F) under %PROGRAMFILES%, which allows local users to gain privileges or obtain maximum control over the product.
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Analysis
by VulDB Data Team • 03/04/2020
The vulnerability identified as CVE-2018-7535 represents a critical privilege escalation flaw in TotalAV version 4.1.7 that stems from improper file system permissions. This issue occurs within the Windows operating system environment where the security model relies on proper access control mechanisms to prevent unauthorized modifications to protected system components. The flaw manifests when the TotalAV installation directory located under the %PROGRAMFILES% environment variable is configured with excessively permissive access controls that grant full file system permissions to all users. This configuration violates fundamental security principles that require least privilege access and proper discretionary access control enforcement. The vulnerability specifically affects the Windows file system permission model where the Everyone group is granted full permissions (F) to the TotalAV installation directory, creating an exploitable entry point for local attackers.
The technical implementation of this vulnerability involves the exploitation of weak discretionary access control lists (DACLs) that govern file and directory access permissions in Windows systems. When an unprivileged user executes malicious code or directly modifies files within the TotalAV installation directory, the system's permission model fails to enforce proper access restrictions. This weakness allows attackers to replace critical executable files, modify configuration settings, or inject malicious code that can execute with the elevated privileges of the TotalAV service. The vulnerability aligns with CWE-276, which describes improper file permissions, and represents a classic case of insecure default permissions that enable unauthorized modification of security-critical components. The flaw operates at the operating system level rather than at the application level, making it particularly dangerous as it bypasses application-specific security controls and directly exploits the underlying file system security model.
The operational impact of this vulnerability extends beyond simple privilege escalation to encompass complete system compromise and potential data exfiltration. Local users who exploit this weakness can gain administrative privileges over the TotalAV application, which may then be used as a foothold for further system compromise. The vulnerability enables attackers to modify the behavior of security software itself, potentially creating backdoors, disabling security features, or installing persistent malware that can operate undetected within the system. This represents a significant concern for enterprise environments where TotalAV is deployed, as it allows any local user to subvert the security protections that the antivirus software is designed to provide. The attack vector is particularly dangerous because it requires no special privileges to execute, making it accessible to any user with local access to the system, and the attack can be automated through simple file system operations that leverage the overly permissive permissions.
Mitigation strategies for CVE-2018-7535 must address the root cause of the weak permissions while maintaining the functionality of the TotalAV application. The primary remediation involves modifying the file system permissions for the TotalAV installation directory to restrict access to only authorized users and processes, typically requiring administrators to explicitly grant access to specific groups or users rather than using broad permissions. System administrators should implement proper access control lists that follow the principle of least privilege, ensuring that only necessary users and services have write access to security software directories. This approach aligns with ATT&CK technique T1068, which covers privilege escalation through local exploitation, and emphasizes the importance of proper system hardening. Organizations should also consider implementing application whitelisting policies, monitoring for unauthorized file modifications, and conducting regular security audits of installed software permissions to identify similar vulnerabilities across their infrastructure. The remediation process requires careful documentation of the original permissions before changes are applied to ensure that legitimate administrative functions continue to operate properly while eliminating the security exposure that allows local privilege escalation.