CVE-2021-44023 in Security
Summary
by MITRE • 12/16/2021
A link following denial-of-service (DoS) vulnerability in the Trend Micro Security (Consumer) 2021 familiy of products could allow an attacker to abuse the PC Health Checkup feature of the product to create symlinks that would allow modification of files which could lead to a denial-of-service.
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Analysis
by VulDB Data Team • 12/22/2021
The vulnerability CVE-2021-44023 represents a critical link following denial-of-service weakness affecting Trend Micro Security Consumer 2021 products including versions 2021.0.1136 and 2021.0.1148. This flaw resides within the PC Health Checkup feature which is designed to scan and analyze system components for potential issues. The vulnerability stems from insufficient validation of symbolic link creation within the software's file handling mechanisms, creating an avenue for malicious exploitation that can ultimately result in system instability and service disruption.
The technical implementation of this vulnerability involves the improper handling of symbolic links within the Trend Micro security suite's file system operations. When the PC Health Checkup feature processes system files, it fails to adequately validate or restrict the creation of symbolic links that could point to critical system files or directories. This weakness allows an attacker to craft malicious symlinks that, when processed by the software, could cause the application to follow these links to unintended locations. The flaw specifically manifests when the software attempts to access or modify files through these symbolic references without proper boundary checking or access control validation.
From an operational perspective, this vulnerability presents significant risk to end-user systems as it can be exploited to trigger denial-of-service conditions through seemingly benign system scans. The attack vector requires minimal privileges and can be executed through crafted file structures that the PC Health Checkup feature would normally process without issue. Once exploited, the vulnerability allows an attacker to manipulate file access patterns that could lead to application crashes, system instability, or complete service unavailability. The impact extends beyond simple service disruption as the vulnerability could potentially be leveraged to escalate privileges or gain unauthorized access to sensitive system components.
Security professionals should consider this vulnerability in the context of CWE-59 and CWE-22 which address improper link following and path traversal issues respectively. The ATT&CK framework categorizes this type of weakness under T1059.001 for command and scripting interpreter and T1068 for local privilege escalation, as the vulnerability could potentially be used to gain elevated system privileges. Organizations should implement immediate mitigations including disabling the PC Health Checkup feature until patches are applied, implementing strict file system access controls, and monitoring for suspicious symlink creation patterns. The vulnerability highlights the importance of proper input validation and secure file handling practices in security software, particularly in consumer-grade products where users may not be aware of the underlying security implications of system scanning features.
The exploitation of this vulnerability demonstrates how legitimate security features can become attack vectors when proper input validation is lacking. Trend Micro's implementation failed to account for the potential for malicious symlinks to be created and processed within their security scanning framework, creating a dangerous feedback loop where the security tool becomes the vector for system compromise. This case underscores the need for comprehensive security testing of all application features, particularly those that interact with the file system, and emphasizes the principle of least privilege in system design. Organizations should conduct thorough vulnerability assessments of their security tooling to identify similar weaknesses that could be exploited by adversaries to gain unauthorized access to their systems.