vm2 through 3.12.0 exposes Node.js's crypto.setFips() function to untrusted guest code when an embedder explicitly allowlists the crypto builtin for a NodeVM (require.builtin: ['crypto']). The builtin sanitizer (sanitizeCryptoModule in lib/builtin.js) replaces crypto.setEngine but leaves crypto.setFips callable, and the readonly wrapper used to expose the host module does not localize side effects of forwarded host functions. Guest code can therefore call crypto.setFips() to change the FIPS mode of the entire host process; the modified mode is subsequently observed by trusted host code (crypto.getFips() changed from 0 to 1 in the reported test), crossing the NodeVM isolation boundary. Fixed in vm2 3.12.1.