A critical security vulnerability (GHSA-864f-rcv7-6rh4) has been disclosed in isolated-vm, a widely-used open-source JavaScript sandbox library with over 2,900 GitHub stars. The flaw affects all versions up to and including 7.0.0 and has not yet been assigned a CVE identifier. The vulnerability allows attackers to escape the isolated sandbox environment and potentially execute code on the host system, enabling remote code execution (RCE). Isolated-vm is commonly used by developers to safely run untrusted JavaScript code in Node.js applications. The sandbox escape nature of this flaw makes it particularly severe, as it undermines the core security guarantee of the library. Users and organizations relying on isolated-vm for security isolation are urged to review their usage and apply patches as they become available.
A critical type confusion vulnerability exists in the isolated-vm Node.js library, specifically in the ExternalCopy class's handling of the transferList option. ExternalCopy is used to securely serialize JavaScript objects out of the host V8 isolate and deserialize them into the guest isolate. The flaw allows code running inside the sandbox to corrupt memory in the host process. The vulnerability was discovered by Endor Labs researcher Cristian-Alexandru Staicu. Exploitation can escalate from a controlled-address crash (reliable denial-of-service via SIGSEGV segmentation fault) all the way to hijacking the host's control flow, enabling a full guest-to-host sandbox escape and potential remote code execution. The vulnerability is triggered starting from a single ivm.Reference, which is the standard mechanism for granting a sandbox any capability. Notably, V8's own Isolate boundary remained intact; the failure was in the C++ glue/binding code that marshals values across the isolate boundary.
Update isolated-vm to version 6.2.0 or 7.0.1, both of which contain patches for this vulnerability. Users with isolated-vm installed in developer environments should prioritize upgrading to the latest patched version. Monitor for unexpected crashes (SIGSEGV segmentation faults) in Node.js host processes that use isolated-vm, as this could indicate exploitation attempts. Review any code that passes ivm.Reference objects into sandboxes, as this is the attack vector. Full exploit details have been withheld by the researchers to prevent malicious use, but users should treat this as a critical update given the potential for RCE.
