CVE-2019-7651 in Anti-Malware
Summary
by MITRE
EPP.sys in Emsisoft Anti-Malware 2018.8.1.8923 allows an attacker to bypass ACLs because Interpreted Device Characteristics lacks FILE_DEVICE_SECURE_OPEN and therefore files and directories "inside" the \\.\EPP device are not properly protected, leading to unintended impersonation or object creation.
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Analysis
by VulDB Data Team • 07/09/2023
The vulnerability identified as CVE-2019-7651 resides within the EPP.sys kernel driver component of Emsisoft Anti-Malware version 2018.8.1.8923, representing a critical access control flaw that fundamentally undermines the security posture of the affected system. This issue manifests through improper device characteristics configuration within the Windows kernel driver framework, specifically in how the driver handles file and directory access permissions for resources located beneath the \.\EPP device namespace. The root cause stems from the Interpreted Device Characteristics implementation lacking the FILE_DEVICE_SECURE_OPEN flag, which is essential for establishing proper security boundaries around device access points. This omission creates a dangerous gap in the kernel's security model where objects within the EPP device namespace become accessible without proper access control enforcement, effectively bypassing the intended access control lists that should govern interactions with these protected resources.
The technical implications of this vulnerability extend beyond simple permission bypass to encompass serious privilege escalation and impersonation capabilities that align with attack patterns documented in the MITRE ATT&CK framework under privilege escalation and persistence techniques. When the FILE_DEVICE_SECURE_OPEN flag is absent, the Windows kernel fails to enforce proper security context checks on operations targeting the EPP device, allowing malicious actors to create, modify, or access files and directories that should normally be restricted to authorized processes only. This flaw enables attackers to perform unauthorized operations against kernel-mode resources that are typically protected by the system's security model, potentially leading to complete system compromise. The vulnerability operates at the kernel level, making it particularly dangerous as it can be leveraged to execute arbitrary code with system-level privileges, bypassing standard user-mode security controls and protections that normally isolate malicious activities.
The operational impact of CVE-2019-7651 represents a significant threat to enterprise security environments where Emsisoft Anti-Malware is deployed, as it transforms a legitimate security tool into a potential attack vector. Organizations utilizing this specific version of Emsisoft software face heightened risk of advanced persistent threats and insider attacks, where adversaries can exploit the vulnerability to establish persistent access or escalate privileges within the compromised system. The vulnerability's nature makes it particularly challenging to detect through conventional means since it operates within the kernel space and leverages legitimate driver functionality to bypass security controls. This characteristic aligns with CWE-284, which specifically addresses improper access control in software systems, and demonstrates how improper device characteristics configuration can lead to severe privilege escalation vulnerabilities. Security professionals must recognize that this vulnerability effectively undermines the security model of the anti-malware solution itself, creating a paradox where the tool designed to protect against malicious software becomes a potential entry point for attackers.
Mitigation strategies for CVE-2019-7651 require immediate action to address the root cause through official vendor patches, as the vulnerability cannot be effectively remediated through configuration changes alone due to its kernel-level nature. Organizations should prioritize updating to Emsisoft Anti-Malware versions that have addressed this specific access control flaw, typically through proper implementation of the FILE_DEVICE_SECURE_OPEN flag in the EPP.sys driver. System administrators should also implement additional monitoring and logging around kernel-mode driver access patterns to detect potential exploitation attempts, particularly focusing on unusual file system operations targeting the EPP device namespace. The vulnerability's classification under ATT&CK techniques for privilege escalation and persistence necessitates comprehensive security monitoring that can identify anomalous behavior patterns consistent with kernel-level attacks. Organizations should also consider implementing additional security controls such as kernel-mode driver signing enforcement and runtime application control policies to limit the potential impact of similar vulnerabilities in other system components. Until the official patch is deployed, security teams should assume that systems running the vulnerable version are at risk of compromise and implement compensating controls to reduce the attack surface and detect potential exploitation attempts.