CVE-2026-47135: vm2 has a sandbox escape via unblocked cross-realm Symbol.for keys + missing bridge write-trap symbol checks

vm2 3.11.2 Symbol.for override in setup-sandbox.js only intercepts 2 of 9 dangerous Node.js cross-realm symbols. Combined with the bridge’s set/defineProperty/deleteProperty traps having no isDangerousCrossRealmSymbol key check, sandbox code can obtain real cross-realm symbols, write them to host objects, and control host-side behavior — verified with a full util.promisify hijack chain.