# CVE-2026-104849: Tinypool: Prototype Pollution Gadget to RCE in run() options

> Prototype pollution allows attackers to inject malicious code into Tinypool worker threads, leading to remote code execution and data manipulation.

- **Severity:** Critical 9.5 (`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`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 2 Oct 2026
- **Updated:** 6 Oct 2026
- **Also known as:** GHSA-85c8-ppgw-ccpr, MINI-gxwj-p3jh-hhmf, MINI-h7jp-5cxp-xjrh, MINI-m3v6-h2vv-mx54, MINI-p77r-ccmp-9pj3, ROOT-APP-NPM-CVE-2026-104849

## What is CVE-2026-104849?

CVE-2026-104849 is a critical code injection vulnerability in tinylibs tinypool, published on 2 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

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.

Weakness: CWE-94 (Improper Control of Generation of Code), CWE-1321 (Improperly Controlled Modification of Object Prototype Attributes)

## Which versions are affected by CVE-2026-104849?

2 open source packages ship an affected version, including tinypool.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `tinypool` | npm | All versions | 2.1.2 |
| `tinypool` | npm | All versions | 2.1.2 |

## How do I fix CVE-2026-104849?

Upgrade tinypool to 2.1.2 or later.

## Is CVE-2026-104849 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-104849 exists.

Public exploit code:

- Offline Tinypool evidence checker for CVE-2026-104849. Worker-pool package and options evidence. Standalone Python; JSON/CSV/HTML reports; no exploit payloads. (github_poc): https://github.com/CompleteTech-Security/tinypool-options-rce-check

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-104849 and fix it if it is affected.

What it is: CVE-2026-104849 is a critical code injection vulnerability in tinylibs tinypool, published on 2 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-104849 exists.

Affected packages and fixed versions:
- tinypool (npm): affected all versions; fixed in 2.1.2
- tinypool (npm): affected all versions; fixed in 2.1.2

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-104849/ (Markdown: https://insights.sbomify.com/CVE-2026-104849/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-104849
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-104849
- OSV: https://osv.dev/vulnerability/CVE-2026-104849

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-104849/
Summaries are generated and may contain mistakes; the official description above is the record.