CVE-2021-23449 in vm2
Summary
by MITRE • 10/18/2021
This affects the package vm2 before 3.9.4. Prototype Pollution attack vector can lead to sandbox escape and execution of arbitrary code on the host machine.
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Analysis
by VulDB Data Team • 10/22/2021
The vulnerability identified as CVE-2021-23449 resides within the vm2 package, a popular Node.js library designed to provide a secure sandbox environment for executing untrusted code. This package operates as a critical component in applications requiring code execution isolation, particularly in serverless computing environments and backend services where third-party code processing is essential. The flaw manifests as a prototype pollution vulnerability that fundamentally undermines the security boundaries intended to protect the host system from malicious code execution. The vulnerability affects all versions prior to 3.9.4, making it a significant concern for systems that have not yet updated their dependencies.
The technical nature of this vulnerability stems from improper handling of prototype properties within the vm2 library's code execution engine. When malicious input is processed through the sandboxed environment, attackers can manipulate the prototype chain of objects, allowing them to pollute the Object.prototype with malicious properties. This prototype pollution occurs during the deserialization or parsing of user-supplied data, where the library fails to properly validate or sanitize object property names. The flaw specifically targets the way the library manages object inheritance and property access, creating a pathway for attackers to bypass sandbox restrictions. According to CWE-471, this represents a weakness in which a program modifies a data structure or object in a way that affects the object's behavior or properties, leading to unintended consequences in the execution environment.
The operational impact of CVE-2021-23449 is severe and potentially catastrophic for affected systems. A successful exploitation of this vulnerability enables attackers to achieve sandbox escape, effectively breaking out of the isolated execution environment that vm2 is designed to provide. Once outside the sandbox, malicious actors can execute arbitrary code on the host machine with the privileges of the Node.js process, potentially leading to complete system compromise. This vulnerability directly maps to ATT&CK technique T1059.007 for Windows and T1059.006 for Unix systems, as it allows for command and scripting interpreter execution. The attack vector typically involves sending specially crafted input through APIs or data processing functions that utilize vm2, where the prototype pollution allows attackers to manipulate the runtime behavior of the Node.js environment. The implications extend beyond simple code execution to include potential data exfiltration, privilege escalation, and persistent backdoor installation.
Mitigation strategies for CVE-2021-23449 focus primarily on immediate version updates to vm2 3.9.4 or later, which includes patches addressing the prototype pollution vulnerability. Organizations should conduct comprehensive dependency audits to identify all systems using vulnerable versions of vm2 and prioritize patching efforts accordingly. Additional protective measures include implementing strict input validation and sanitization at all entry points where user data is processed, employing runtime monitoring to detect anomalous behavior patterns, and establishing network segmentation to limit the potential impact of successful exploitation. Security teams should also consider implementing application firewalls and intrusion detection systems to monitor for exploitation attempts. The vulnerability highlights the critical importance of maintaining up-to-date dependencies and following secure coding practices, particularly when dealing with sandboxed environments. Organizations should also consider alternative approaches such as using more secure sandboxing solutions or implementing additional layers of security controls to reduce the attack surface and provide defense-in-depth strategies against similar vulnerabilities.