CVE-2021-42011 in Apex One
Summary
by MITRE • 10/21/2021
An incorrect permission assignment vulnerability in Trend Micro Apex One and Apex One as a Service could allow a local attacker to load a DLL with escalated 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.
If you want to get the best quality for vulnerability data then you always have to consider VulDB.
Analysis
by VulDB Data Team • 10/28/2021
The vulnerability identified as CVE-2021-42011 represents a critical permission assignment flaw within Trend Micro Apex One and its cloud-based service Apex One as a Service. This weakness stems from improper privilege management during dynamic link library loading processes, creating an avenue for local attackers to escalate their system access. The vulnerability specifically affects systems where Trend Micro Apex One is installed and running with elevated privileges, making it particularly dangerous in enterprise environments where security software typically operates with administrative rights to perform comprehensive threat detection and remediation tasks.
The technical exploitation of this vulnerability relies on a fundamental flaw in how the software handles dynamic library loading operations. When the Trend Micro service executes, it loads external libraries without proper validation of the library's origin or permissions, creating a condition where an attacker can substitute a malicious DLL for a legitimate one. This occurs because the software does not properly verify the integrity or authorization status of libraries before execution, allowing arbitrary code to be loaded with the elevated privileges of the Trend Micro service itself. The vulnerability manifests as a privilege escalation vector where a low-privileged user can effectively gain administrative access through this indirect method of code execution.
From an operational perspective, the impact of CVE-2021-42011 extends beyond simple privilege escalation to encompass potential system compromise and data exfiltration capabilities. Since Trend Micro Apex One typically operates with broad system access rights, successful exploitation could provide attackers with complete control over endpoint systems, including the ability to modify system files, install additional malware, or establish persistent backdoors. The vulnerability's requirement for initial low-privileged code execution means that attackers would need to first gain some foothold through other means such as phishing attacks, unpatched software vulnerabilities, or social engineering techniques before leveraging this specific weakness.
Security professionals should note that this vulnerability aligns with CWE-276, which addresses incorrect permission assignment in software systems. The flaw demonstrates how improper access control mechanisms can create dangerous privilege escalation opportunities, particularly in security software that operates with elevated system rights. Organizations should consider implementing the ATT&CK framework's T1055 technique for process injection as a detection method, since the exploitation pattern mirrors unauthorized DLL loading behaviors. The vulnerability also highlights the importance of least privilege principles in security software deployment, where protection tools should not operate with unnecessary elevated privileges that could be exploited by attackers.
Mitigation strategies should focus on immediate patch application from Trend Micro, which addresses the core permission assignment flaw in the software's library loading mechanism. Organizations should also implement additional monitoring for unusual DLL loading patterns, particularly those occurring in the context of Trend Micro processes. Network segmentation and endpoint detection and response solutions can help identify exploitation attempts by monitoring for unauthorized privilege escalation activities. Regular security assessments should verify that Trend Micro services are running with appropriate privilege levels and that no unnecessary elevated rights exist for the software's operational context. The vulnerability serves as a reminder of the critical importance of secure coding practices, particularly in security software where improper privilege management can create the very vulnerabilities that the software is designed to prevent.