CVE-2022-3859 is a medium-severity vulnerability identified in the Trellix Agent (TA) for Windows versions prior to 5.7.8. The vulnerability is classified as CWE-427, which pertains to an uncontrolled search path element. Specifically, the issue arises because the Trellix Agent improperly handles the search path for DLLs, allowing an attacker with administrative privileges to place a malicious DLL in the Windows System folder. Since the Windows System folder is a protected directory, only users with admin rights can write to it. However, once a malicious DLL is placed there, the Trellix Agent can be tricked into loading this DLL, resulting in privilege escalation from an administrative user to the SYSTEM account, which has the highest level of privileges on a Windows system. This elevation of privilege can enable an attacker to execute arbitrary code with SYSTEM-level permissions, potentially leading to full system compromise. The vulnerability requires the attacker to already have administrative access to the system, which limits the initial attack vector but significantly increases the impact if exploited. There are no known exploits in the wild as of the published date (November 30, 2022), and no official patches or mitigation links were provided in the source information. The vulnerability affects Trellix Agent versions 5.x prior to 5.7.8, and the issue is specific to Windows operating systems. The vulnerability was reserved and disclosed by Trellix in early November 2022 and is recognized by CISA as an enriched vulnerability, indicating its relevance for cybersecurity monitoring and response.

For European organizations using Trellix Agent on Windows endpoints, this vulnerability presents a significant risk primarily in environments where administrative privileges are not tightly controlled. An attacker who gains administrative access—potentially through other means such as phishing, credential theft, or insider threat—could exploit this vulnerability to escalate privileges to SYSTEM level. This could lead to full control over affected systems, enabling the attacker to disable security controls, install persistent malware, exfiltrate sensitive data, or disrupt operations. Given that Trellix Agent is a security product often deployed in enterprise environments for endpoint protection, exploitation could undermine the security posture of the organization by compromising the very tool meant to defend it. The impact is particularly critical in sectors with stringent data protection requirements such as finance, healthcare, and critical infrastructure, where SYSTEM-level compromise can lead to severe regulatory and operational consequences. However, the requirement for initial administrative access limits the scope of exploitation, making this vulnerability more of a post-compromise escalation vector rather than a direct remote attack. Organizations with mature privilege management and endpoint security monitoring may detect and prevent exploitation attempts more effectively. Nonetheless, the potential for privilege escalation to SYSTEM level makes this vulnerability a serious concern for maintaining endpoint integrity and trustworthiness.

1. Upgrade Trellix Agent to version 5.7.8 or later where this vulnerability is addressed. Since no patch links were provided, organizations should contact Trellix support or check official Trellix update channels for the latest secure versions. 2. Enforce strict administrative privilege management: limit the number of users with admin rights on Windows systems and implement just-in-time (JIT) or just-enough-administration (JEA) principles to reduce the attack surface. 3. Monitor and audit the Windows System folder and other protected directories for unauthorized DLL additions or modifications using file integrity monitoring tools. 4. Implement application whitelisting to prevent unauthorized DLLs from loading, especially in critical system folders. 5. Use endpoint detection and response (EDR) solutions to detect suspicious DLL loading behaviors and privilege escalation attempts. 6. Conduct regular security awareness training to reduce the risk of initial compromise that could lead to administrative access. 7. Employ multi-factor authentication (MFA) for administrative accounts to reduce the risk of credential theft leading to admin access. 8. Review and harden Group Policy Objects (GPOs) and system configurations to restrict DLL search paths and loading behavior where possible. 9. Maintain an incident response plan that includes procedures for detecting and responding to privilege escalation attacks.