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Sandbox Escape in vm2 via Host Object Exposure
CVE-2026-43997 is a critical sandbox escape vulnerability in vm2, the Node.js sandbox library used to execute untrusted JavaScript. In affected versions prior to 3.11.0, sandboxed code can obtain a reference to the host Object from outside the intended isolation boundary. Once a genuine host object is exposed inside the sandbox, the attacker can leverage host-side functionality to break out of vm2’s proxy-based protections and execute code in the host context. One documented exploitation path involves calling getOwnPropertySymbols on the exposed host object to retrieve the custom inspect symbol used by Node.js internals, demonstrating access to a real host object rather than a sanitized proxy. The flaw is fixed in vm2 3.11.0.
What it means and what to do now: patch path, interim mitigations, and the assume-compromise checklist.
What an attacker gets, and what they’ve been doing with it.
Successful exploitation breaks vm2’s isolation guarantees and allows sandbox escape from untrusted JavaScript into the host Node.js environment. Because the vulnerability exposes a host object directly, an attacker can pivot from sandboxed execution to arbitrary code execution in the host process. This can result in full compromise of the application context running vm2, including unauthorized access to sensitive data, modification of application state, execution of arbitrary commands through the host runtime, and disruption of service availability.
If you can’t patch tonight, do this now.
If immediate patching is not possible, reduce or eliminate exposure by preventing untrusted or attacker-controlled JavaScript from being executed through vm2. Restrict access to any application features, APIs, automation workflows, plugin systems, or agent frameworks that pass untrusted code into the sandbox. Where strong isolation is required, use stronger containment boundaries such as process isolation, containers, microVMs, or V8 isolate-based designs rather than relying solely on vm2’s JavaScript-level sandboxing.
Patch, then assume compromise.
Upgrade vm2 to version 3.11.0 or later, as the vulnerability is fixed in 3.11.0. Given the broader pattern of critical vm2 sandbox-escape issues reported in 2026, upgrading to the latest available maintained release is preferable where possible. Security teams should also review any deployments that rely on vm2 for execution of untrusted code and validate that no affected versions remain in use.
No public exploits tracked yet. Mallory keeps watching.
Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.
12 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.