CVE-2026-47210: vm2 sandbox escape via JSPI-backed Promise `.finally()` species bypass

Should you act?

Critical and remotely reachable

No known exploitation yet, but it is network-reachable without credentials. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.

• Not in CISA KEV, but CISA’s SSVC assessment records a public proof-of-concept, so attack code exists.
• EPSS 0.8%, percentile 57: FIRST’s model estimates a 0.8% chance of exploitation activity in the next 30 days, higher than 57% of all scored CVEs (moderate). EPSS is a probability, not a verdict.
• Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
• Only applies if your dependency tree includes vm2 (npm) <= 3.11.3, fixed in 3.11.4. Check your lockfile, including transitive dependencies.

What it is

vm2 is an open source vm/sandbox for Node.js. Prior to version 3.11.4, a sandbox escape vulnerability in vm2 allows arbitrary code execution in the host process when untrusted code is executed with async support on runtimes exposing WebAssembly JSPI (WebAssembly.promising / WebAssembly.Suspending). In the tested configuration, a JSPI-backed Promise can reach Promise.prototype.finally() in a way that bypasses the expected Promise-species hardening and exposes a host-originated rejection object to attacker-controlled species logic, breaking the sandbox boundary. This issue has been patched in version 3.11.4.

From the GitHub advisory

Summary A sandbox escape vulnerability in vm2 allows arbitrary code execution in the host process when untrusted code is executed with async support on runtimes exposing WebAssembly JSPI (WebAssembly.promising / WebAssembly.Suspending). In the tested configuration, a JSPI-backed Promise can reach Promise.prototype.finally() in a way that bypasses the expected Promise-species hardening and exposes a host-originated rejection object to attacker-controlled species logic, breaking the sandbox boundary.

This is a critical sandbox escape: any application that treats vm2 as a security boundary may be fully compromised.

Details

On node26, JSPI-backed Promises created through WebAssembly.promising(...) do not behave like ordinary sandbox Promises.

That path yields a host-originated TypeError during JSPI processing. Inside attacker-controlled species logic reached through .finally(), the rejection object exposes a usable host constructor chain. In the tested environment, the rejection object's constructor path can be used to reach host process, which leads to arbitrary code execution in the host process.

Weakness type: CWE-913.

Product: vm2 (npm) · Assigned by: GitHub_M · Published: 2026-06-12

Affected and fixed versions

Severity scores

• Attack vector: network (remotely reachable)
• Attack complexity: low
• Privileges required: none (no login)
• User interaction: none
• Scope: unchanged

CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.

Exploitation and urgency

• CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
• CISA SSVC assessment: exploitation poc, automatable yes, technical impact total.
• FIRST EPSS (model of 2026-10-21): 0.82% probability of exploitation activity in the next 30 days; percentile 57.

Timeline

• 2026-05-29 — GitHub-reviewed advisory GHSA-6j2x-vhqr-qr7q published (critical)
• 2026-06-12 — CVE record published by GitHub_M
• 2026-06-13 — CVE record last updated

Sources and references

Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.

Vulnerability records

1. GitHub Advisory GHSA-6j2x-vhqr-qr7q github.com
2. CVE.org record CVE-2026-47210 cve.org
3. NVD entry CVE-2026-47210 nvd.nist.gov

Other references from the CVE record and advisory

1. github.com github.com
2. github.com github.com
3. github.com github.com

Critical npm advisories · Today’s Security Digest