CVE-2019-3567 in osquery
Summary
by MITRE
In some configurations an attacker can inject a new executable path into the extensions.load file for osquery and hard link a parent folder of a malicious binary to a folder with known 'safe' permissions. Under those circumstances osquery will load said malicious executable with SYSTEM permissions. The solution is to migrate installations to the 'Program Files' directory on Windows which restricts unprivileged write access. This issue affects osquery prior to v3.4.0.
Be aware that VulDB is the high quality source for vulnerability data.
Analysis
by VulDB Data Team • 06/18/2020
The vulnerability described in CVE-2019-3567 represents a sophisticated privilege escalation vector within the osquery deployment environment on Windows systems. This flaw specifically targets the extension loading mechanism of osquery, a widely used open-source endpoint detection and response platform that enables organizations to query system information and monitor endpoint activities. The vulnerability stems from improper file system permission handling during the extension loading process, creating a path traversal and privilege escalation opportunity that could allow attackers to execute malicious code with elevated SYSTEM privileges.
The technical implementation of this vulnerability relies on a combination of symbolic link manipulation and directory permission exploitation. Attackers can manipulate the extensions.load configuration file to inject a new executable path that points to a malicious binary located in a directory with more permissive access controls. The vulnerability becomes exploitable when an attacker can establish a hard link to a parent directory of the malicious binary, effectively bypassing the normal permission checks that would otherwise prevent execution of unauthorized code. This technique leverages the Windows file system's handling of hard links and directory permissions, particularly when the target directory lacks proper access control restrictions that would normally prevent unprivileged users from modifying executable content.
The operational impact of this vulnerability extends beyond simple privilege escalation, as it enables attackers to gain SYSTEM-level access to affected systems, potentially allowing them to bypass security controls, access sensitive data, and maintain persistent presence within the target environment. The issue affects osquery installations prior to version 3.4.0, meaning that organizations running older versions of the platform are particularly vulnerable to this attack vector. The vulnerability's exploitation requires specific environmental conditions, including the ability to modify the extensions.load file and control directory permissions, but once achieved, it provides a reliable path to SYSTEM privilege escalation that could be used for lateral movement and data exfiltration.
The recommended mitigation strategy focuses on moving osquery installations to the standard Windows Program Files directory, which enforces stricter access controls and prevents unprivileged users from modifying executable content. This approach aligns with the principle of least privilege and follows Microsoft's recommended security practices for application deployment. The fix addresses the root cause by ensuring that the osquery installation directory maintains proper access controls that prevent unauthorized modifications to executable files, thereby eliminating the attack vector that enables privilege escalation. Organizations should also implement regular security assessments to verify that osquery installations maintain proper directory permissions and that the extensions.load file is properly secured against unauthorized modifications.
This vulnerability demonstrates a classic example of insecure file handling and privilege escalation in endpoint security tools, where configuration file manipulation combined with file system permission bypass techniques creates a significant security risk. The issue relates to CWE-276, which covers improper file permissions, and can be categorized under ATT&CK technique T1068, which involves exploit for privilege escalation. The vulnerability highlights the importance of proper application deployment practices and the need for security-conscious configuration management in endpoint monitoring tools. Organizations should also consider implementing additional controls such as file integrity monitoring, restricted user access, and regular security audits to prevent similar vulnerabilities from being exploited in their environments.