CVE-2026-92955 in vm2
Summary
by MITRE • 09/17/2026
vm2 before 3.11.8 contains a sandbox escape vulnerability in NodeVM that allows attackers to access the host __proto__ getter/setter through console._stdout and console._stderr. Attackers can overwrite EventEmitter.prototype.emit and trigger process events to execute code with process context, bypassing code generation restrictions.
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Analysis
by VulDB Data Team • 09/17/2026
The vulnerability identified in versions of vm2 prior to 3.11.8 represents a critical sandbox escape within the NodeVM implementation, fundamentally undermining the isolation guarantees that such environments are designed to provide. In secure application architectures, virtual machines or sandboxes are utilized to execute untrusted code without granting it access to sensitive host resources, system processes, or internal object properties. However, this flaw allows an attacker to bypass these restrictions by exploiting specific console objects exposed within the sandboxed environment. Specifically, the vulnerability leverages the ability to access and manipulate the _proto_ getter and setter through the console._stdout and console._stderr streams. By interacting with these prototype chains, a malicious actor can effectively break out of the restricted context and gain elevated privileges that extend beyond the intended boundaries of the virtual machine.
The technical mechanism behind this exploitation involves manipulating JavaScript's prototype inheritance model to overwrite critical methods on global objects. Once access to the host _proto_ is achieved through the console streams, the attacker targets EventEmitter.prototype.emit. By overwriting this method, the attacker gains control over how events are processed and dispatched within the Node.js runtime environment. This manipulation allows for the triggering of process-level events that execute code with full process context rather than being confined to the sandboxed scope. Consequently, restrictions on code generation or execution paths intended by the vm2 library are effectively neutralized, as the attacker can now invoke functions and access objects that were previously inaccessible from within the isolated environment.
The operational impact of this vulnerability is severe, particularly in scenarios where user-supplied input is processed using NodeVM for security isolation. If an application relies on vm2 to sandbox untrusted scripts, such as those generated by users or received from external sources, a successful exploit could lead to remote code execution with the same privileges as the underlying Node.js process. This can result in full system compromise, data exfiltration, lateral movement within internal networks, and denial of service through resource exhaustion. The ability to bypass code generation restrictions means that even if input validation or sanitization measures are in place at a higher level, the core security mechanism provided by the sandbox is rendered ineffective once this prototype pollution vector is triggered.
To mitigate this risk, organizations utilizing vm2 must immediately upgrade to version 3.11.8 or later, where these specific escape vectors have been addressed and patched. For environments that cannot be updated instantly due to dependency constraints, it is advisable to implement strict input validation and sanitization strategies for any data passed into the sandboxed context. Additionally, deploying runtime application self-protection tools or web application firewalls with capabilities to detect prototype pollution attacks can provide an additional layer of defense. Monitoring logs for unusual activity related to EventEmitter manipulation or unexpected process event triggers may also aid in early detection of exploitation attempts. This vulnerability is categorized under CWE-94 as Improper Control of Generation of Code and CWE-1321 as Prototype Pollution, reflecting its nature as a code injection via prototype manipulation. In the context of the MITRE ATT&CK framework, this exploit aligns with techniques involving command and script interpretation through sandbox escape mechanisms, highlighting the importance of maintaining up-to-date dependencies in security-critical applications.