CVE-2026-92934 in vm2
Summary
by MITRE • 09/17/2026
vm2 before 3.11.8 contains an incomplete fix for Error.cause sanitization that allows sandbox escape when revisited host-wrapped AggregateError objects are caught within a single exception handler traversal. Attackers can exploit cycle detection bypass in handleException to access unsanitized host proxies embedded in the errors array, enabling full remote code execution and process information disclosure from the sandbox.
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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 failure in the security model designed to isolate untrusted JavaScript code within a sandboxed environment. This issue stems from an incomplete remediation effort regarding Error.cause sanitization, which is intended to prevent malicious actors from accessing sensitive host objects through error handling mechanisms. The core technical flaw lies in how the library processes AggregateError objects that have been wrapped by the host environment and subsequently caught during exception handling. Specifically, when such errors are revisited within a single traversal of an exception handler, the internal cycle detection logic fails to properly sanitize or isolate these complex error structures. This oversight allows attackers to bypass security controls that rely on detecting circular references or recursive patterns in object graphs, thereby exposing underlying host proxies that were meant to remain inaccessible from within the sandboxed context.
From a technical perspective, this vulnerability exploits the handleException function's inability to correctly identify and neutralize unsanitized host proxies embedded within the errors array of an AggregateError. In normal operation, vm2 is designed to strip or restrict access to any objects that originate from the host environment to maintain strict isolation between the sandboxed code and the underlying Node.js process. However, due to the incomplete fix for Error.cause handling, specific sequences involving caught exceptions can trick the sanitizer into retaining references to these dangerous proxies. By leveraging this cycle detection bypass, an attacker can construct a payload that manipulates how errors are processed during runtime, effectively breaking out of the restricted execution context. This breakout mechanism is particularly insidious because it does not require direct access to global objects but instead relies on the nuanced behavior of JavaScript's error propagation and handling mechanisms.
The operational impact of this vulnerability is severe, as it enables full remote code execution within the host process running vm2. Once an attacker successfully escapes the sandbox through this mechanism, they gain unrestricted access to the Node.js environment, which typically includes capabilities such as file system interaction, network communication, and arbitrary command execution depending on the privileges of the hosting application. Furthermore, the vulnerability facilitates significant information disclosure, allowing attackers to extract sensitive process data that should remain confined within the security boundary of the sandbox. This level of compromise can lead to broader systemic risks, including data exfiltration, lateral movement in a networked environment, and complete takeover of the server or service relying on vm2 for code execution isolation.
In terms of industry classification standards, this vulnerability aligns with CWE-78 Improper Neutralization of Special Elements used in an OS Command (OS Injection) when considering the outcome of remote code execution, but more accurately reflects CWE-94 Improper Control of Generation of Code (Code Injection) and CWE-200 Exposure of Sensitive Information to an Unauthorized Actor due to the information disclosure aspect. The exploitation technique maps closely to MITRE ATT&CK techniques related to Defense Evasion, specifically T1620 Reflection-based Evasion where attackers use legitimate system features like error handling to bypass security controls, as well as T1059 Command and Scripting Interpreter for executing arbitrary code after gaining access. These mappings highlight the sophisticated nature of the attack vector which abuses standard language semantics rather than relying on traditional buffer overflows or memory corruption errors.
To mitigate this risk, organizations utilizing vm2 must immediately upgrade to version 3.11.8 or later where the incomplete fix has been properly addressed and cycle detection logic in exception handling is hardened against such bypasses. For environments that cannot update immediately due to dependency constraints, implementing additional sandboxing layers using containerization technologies like Docker or Kubernetes can provide a secondary defense-in-depth measure by limiting the impact of any potential breakout from the JavaScript runtime. Additionally, application developers should audit their use of vm2 to ensure that no untrusted code is executed with elevated privileges and consider alternative libraries if the specific features requiring this version are not strictly necessary. Regular security assessments focused on dependency management and sandbox integrity testing are essential to prevent similar vulnerabilities in future deployments.