{"id":"CVE-2026-102992","aliases":["GHSA-67c8-pqhq-4rmx"],"url":"https://o3.security/vulnerability/CVE-2026-102992","summary":"piscina: Prototype-pollution gadget in ThreadPool.options allows RCE via execArgv / loadBalancer / env","details":"### Summary\n\nA prototype-pollution gadget in `ThreadPool.options` allows an attacker who can pollute `Object.prototype` to execute arbitrary code in Piscina worker threads, invoke arbitrary functions during task scheduling, or inject environment variables into workers. The root cause is that `ThreadPool.options` is created as a plain object inheriting from `Object.prototype`, so any option without an explicit default in `kDefaultOptions` can be supplied via the prototype chain.\n\n### Details\n\nIn `src/index.ts` the `ThreadPool` constructor builds the resolved options object as a plain object:\n\n```ts\nthis.options = { ...kDefaultOptions, ...options, filename, maxQueue: 0 }\n```\n\nBecause this object has `Object.prototype` as its prototype, reads for properties that are not own properties of the object and are not present in `kDefaultOptions` fall back to `Object.prototype`. This means a prototype-pollution primitive (e.g. from a vulnerable `merge()` or `JSON.parse` merge elsewhere in the application) can inject values for `execArgv`, `env`, `loadBalancer`, `argv`, `workerData`, `resourceLimits`, `niceIncrement`, `closeTimeout`, `recordTiming`, `stricterFIFO`, `workerHistogram`, and `trackUnmanagedFds`.\n\nThe most serious gadget is `execArgv`, which is passed directly to `new Worker(..., { execArgv })`. An attacker can set `Object.prototype.execArgv = ['--require', '/tmp/attacker.js']`, causing every worker to preload and execute the attacker-controlled module on startup.\n\nThis issue survived the fix for **GHSA-x9g3-xrwr-cwfg / CVE-2026-55388** (\"Prototype Pollution Gadget → RCE via inherited options.filename\"). That advisory hardened the `Piscina` constructor's `filename` read and `run()`'s `filename`/`name` reads, but `ThreadPool.options` itself was not created with a null prototype. The same class of attack is therefore still possible against any option without an explicit default in `kDefaultOptions`.\n\n### PoC\n\n```js\nimport { resolve } from 'node:path'\nimport Piscina from 'piscina'\n\nObject.prototype.execArgv = ['--require', '/tmp/attacker.js']\n\nconst pool = new Piscina({\n  filename: resolve(import.meta.dirname, 'worker.js'),\n  minThreads: 1,\n  maxThreads: 1,\n})\n\nawait pool.run(1)\n```\n\n`/tmp/attacker.js` is executed in the worker on startup. A full reproduction repository with `execArgv`, `loadBalancer`, and `env` vectors is available at https://github.com/Fcmam5/piscina-pp-poc.\n\n### Impact\n\n- **Remote Code Execution**: via `execArgv` (arbitrary `--require` module preloaded in every worker on spawn).\n- **Arbitrary code execution in the main thread**: via `loadBalancer`, an attacker-supplied function that is called during task scheduling.\n- **Environment/CLI option injection**: via `env`, which is passed to each worker constructor.\n- **Denial of Service / unexpected behavior**: via other reachable options such as `workerData`, `resourceLimits`, `niceIncrement`, `closeTimeout`, `recordTiming`, etc.\n\nAnyone using Piscina in an application where `Object.prototype` can be polluted (e.g. through a dependency with a prototype-pollution vulnerability) is impacted.","published":"2026-09-30T19:50:18.036Z","modified":"2026-10-21T02:54:30.091235360Z","cvss":null,"epss":null,"cisaKev":null,"exploitsKnown":null,"affectedPackages":[{"ecosystem":"npm","name":"piscina","fixedVersion":"5.3.2"},{"ecosystem":"npm","name":"piscina","fixedVersion":"4.9.4"},{"ecosystem":"npm","name":"piscina","fixedVersion":"6.0.0-rc.5"}],"fix":{"url":"https://github.com/piscinajs/piscina/commit/0cb12fca37f526065b072592afe954574dcc656f","label":"piscinajs/piscina@0cb12fc"},"references":[{"type":"WEB","url":"https://github.com/piscinajs/piscina/releases/tag/v4.9.4"},{"type":"WEB","url":"https://github.com/piscinajs/piscina/releases/tag/v5.3.2"},{"type":"WEB","url":"https://github.com/piscinajs/piscina/releases/tag/v6.0.0-rc.5"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/102xxx/CVE-2026-102992.json"},{"type":"ADVISORY","url":"https://github.com/piscinajs/piscina/security/advisories/GHSA-67c8-pqhq-4rmx"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-102992"},{"type":"FIX","url":"https://github.com/piscinajs/piscina/commit/0cb12fca37f526065b072592afe954574dcc656f"},{"type":"FIX","url":"https://github.com/piscinajs/piscina/commit/2f69f67159a0e48b38fd61fa4a91c2fdc19fff72"},{"type":"FIX","url":"https://github.com/piscinajs/piscina/commit/5be7bbb19e3787bb698862cd516121a578d690f7"},{"type":"FIX","url":"https://github.com/piscinajs/piscina/commit/bebbda255c2981cecddd36b171b94be2fd41c9a6"},{"type":"PACKAGE","url":"https://github.com/piscinajs/piscina"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-10-21T02:54:30.091235360Z"}}