# CVE-2026-93606: vm2 sandbox escape via Promise Symbol.species hijack

Source: https://junglewise.ai/threats/cve-2026-93606-vm2-sandbox-escape-via-promise-symbol-species-hijack  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-18. Updated: 2026-09-26  
License: CC BY 4.0 with a link back

CVE-2026-93606 · Severity: critical · CVSS 10 · Published 2026-09-18

vm2 is a popular npm library that runs untrusted JavaScript code in an isolated sandbox environment. This vulnerability allows sandboxed code to break out of the isolation and execute arbitrary code on the host system by manipulating how the library handles rejected promises. An attacker can gain full control over the host machine, including executing system commands and accessing sensitive data.

Technologies: [vm2 (npm)](https://junglewise.ai/threats/technologies/vm2). Vendors: [npm](https://junglewise.ai/threats/vendors/npm).

## Quick answers

**Is CVE-2026-93606 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-93606 being exploited in the wild.

**How severe is CVE-2026-93606?** Critical severity, with a CVSS score of 10, published 18 September 2026.

**Which products and versions are affected?** vm2 (npm) 3.12.0 and earlier.

**Is there a fix for CVE-2026-93606?** A patch was published on 2026-09-18: Fix released in version 3.12.1 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-93606 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-93606?** Check whether you run vm2 (npm) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

The vulnerability is a sandbox escape in vm2's promise rejection sanitizer. When an embedder exposes a host-realm Promise to the sandbox, vm2 attempts to sanitize rejection values via lib/bridge.js functions (hostPromiseSanitizeReject, makeSanitizedPromiseCallback, normalizeHostPromiseCallbacks). However, two gaps combine to bypass this: (1) the sandbox-side Symbol.species/.then neutralization is installed only on the sandbox intrinsic Promise.prototype, never applying to host Promises; (2) the rejection sanitizer only wraps then/catch slots when they hold a function—calling p.then() with no onRejected handler causes V8 to substitute its internal Thrower, which re-throws the raw host rejection. By hijacking p.constructor[Symbol.species] on the host Promise, an attacker captures V8's raw resolve/reject closures and receives an unsanitized bridge proxy of the host object, completely bypassing handleException and hostPromiseSanitizeReject. If the rejection value is host-pivotable (e.g., the host process object), this results in host RCE. The fix is available in version 3.12.1.

## Affected products

- npm vm2 3.12.0 and earlier

## Timeline

- 2026-09-18: disclosed: CVE-2026-93606 published
- 2026-09-18: patched: Fix released in version 3.12.1

## References

- [https://github.com/patriksimek/vm2/security/advisories/GHSA-6454-5x88-m6jw](https://github.com/patriksimek/vm2/security/advisories/GHSA-6454-5x88-m6jw)
- [https://www.vulncheck.com/advisories/vm2-before-3.12.1-sandbox-escape-via-promise-symbol-species](https://www.vulncheck.com/advisories/vm2-before-3.12.1-sandbox-escape-via-promise-symbol-species)

## Related threats

- [vm2 NodeVM path bypass in custom resolution](https://junglewise.ai/threats/duplicate-advisory-vm2-nodevm-custom-resolution-bypasses-external-path-5d3a7272)
- [vm2 NodeVM zlib buffer pool information disclosure](https://junglewise.ai/threats/duplicate-advisory-vm2-nodevm-zlib-buffers-expose-pooled-host-memory-6007c734)
- [vm2 host Promise rejection denial of service in construct trap](https://junglewise.ai/threats/duplicate-advisory-vm2-host-promise-rejection-from-an-exposed-f7aba6ba)
- [vm2 sandbox escape via Buffer backing-store ownership bypass](https://junglewise.ai/threats/cve-2026-100723-vm2-before-3-12-2-does-not-apply-its-buffer-backing-store)
- [vm2 unhandled Promise rejection in construct trap](https://junglewise.ai/threats/cve-2026-100722-vm2-before-3-12-2-does-not-apply-host-side-promise-rejection)