Source: security@trendmicro.com
A security agent link following vulnerability in Trend Micro Apex One could allow a local attacker to escalate privileges on affected installations. Please note: an attacker must first obtain the ability to execute low-privileged code on the target system in order to exploit this vulnerability.
Trend Micro Apex One is vulnerable to a privilege escalation attack. A local attacker, after gaining initial code execution, can exploit a link following vulnerability to elevate their privileges to a higher level, potentially gaining system-level access and control over the affected system.
Step 1: Initial Compromise: The attacker must first gain the ability to execute low-privileged code on the target system. This could be achieved through various means, such as exploiting another vulnerability, social engineering, or a compromised user account.
Step 2: Link Creation: The attacker crafts a malicious link (e.g., a symbolic link or a hard link) that points to a sensitive system resource or a file the attacker can control. The target of the link is chosen to facilitate privilege escalation.
Step 3: Triggering the Vulnerability: The attacker triggers the vulnerability by causing the Trend Micro Apex One security agent to interact with the malicious link. This could involve placing the link in a location monitored by the agent, or by tricking the agent into scanning the link.
Step 4: Privilege Escalation: The security agent, due to the link following vulnerability, follows the malicious link and performs an action (e.g., file read, file write, or code execution) with elevated privileges, as it is running with higher permissions. This allows the attacker to gain control of the system.
The vulnerability lies within the security agent's handling of links or symbolic links. The agent likely processes files or directories in a way that allows an attacker to control the target of a link. By crafting a malicious link that points to a sensitive system resource or a file the attacker can control, they can trick the agent into performing actions with elevated privileges. The root cause is likely a failure to properly validate the target of the link before performing an operation on it, leading to a path traversal or arbitrary file write/read vulnerability. This could involve a lack of proper input validation or insufficient checks on the link's target, allowing the attacker to bypass security restrictions. The specific function or logic flaw is likely related to how the agent resolves or follows links during file scanning, update processes, or other privileged operations. The lack of proper sanitization or validation of the link target allows for the execution of arbitrary code with elevated privileges.
While no specific APTs are directly linked at this time, any threat actor with the capability to perform local privilege escalation would be interested in this vulnerability. This includes actors involved in ransomware, espionage, and financial crime. The vulnerability is likely to be quickly integrated into existing exploit kits. CISA KEV status is highly probable once exploitation is observed.
Monitor file system activity for the creation of suspicious links, especially those pointing to system directories or sensitive files.
Analyze security agent logs for unusual file access patterns or error messages related to link following.
Implement host-based intrusion detection systems (HIDS) to detect suspicious process behavior or file modifications.
Monitor network traffic for any unusual communication patterns originating from the affected system.
Review system logs for evidence of unauthorized privilege escalation attempts.
Apply the latest security patches provided by Trend Micro immediately.
Implement a least-privilege access model for all user accounts.
Regularly audit system configurations and security settings.
Disable or restrict the use of symbolic links if possible, or implement strict validation of link targets.
Implement file integrity monitoring to detect unauthorized file modifications.
Review and harden the security agent's configuration to minimize its attack surface.
Conduct regular vulnerability scans and penetration tests to identify and address security weaknesses.