# CVE-2020-36632: hughsk flat index.js unflatten prototype pollution

> Prototype pollution in the flat library allows remote attackers to modify object prototypes, potentially leading to code execution or privilege escalation.

- **Severity:** Medium 6.3 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 25 Dec 2022
- **Updated:** 4 Aug 2024
- **Also known as:** CLSA-2026-1771546205, GHSA-2j2x-2gpw-g8fm, ROOT-APP-NPM-CVE-2020-36632, UBUNTU-CVE-2020-36632

## What is CVE-2020-36632?

CVE-2020-36632 is a medium-severity vulnerability in hughsk flat, published on 25 Dec 2022. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

A vulnerability, which was classified as critical, was found in hughsk flat up to 5.0.0. This affects the function unflatten of the file index.js. The manipulation leads to improperly controlled modification of object prototype attributes ('prototype pollution'). It is possible to initiate the attack remotely. Upgrading to version 5.0.1 is able to address this issue. The name of the patch is 20ef0ef55dfa028caddaedbcb33efbdb04d18e13. It is recommended to upgrade the affected component. The identifier VDB-216777 was assigned to this vulnerability.

Weakness: CWE-1321 (Improperly Controlled Modification of Object Prototype Attributes)

## Which versions are affected by CVE-2020-36632?

10 open source packages ship an affected version, including flat. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `flat` | npm | All versions | 1.6.2 |
| `flat` | npm | All versions | 1.6.2 |
| `flat` | npm | From 2.0.0 | 2.0.2 |
| `flat` | npm | From 2.0.0 | 2.0.2 |
| `flat` | npm | From 3.0.0 | 3.0.1 |
| `flat` | npm | From 3.0.0 | 3.0.1 |
| `flat` | npm | From 4.0.0 | 4.0.2 |
| `flat` | npm | From 4.0.0 | 4.0.2 |
| `flat` | npm | From 5.0.0 | 5.0.1 |
| `flat` | npm | From 5.0.0 | 5.0.1 |

Products: Flat Project Flat.

## How do I fix CVE-2020-36632?

Upgrade flat to a fixed version for your release line: 1.6.2, 2.0.2, 3.0.1 or 4.0.2.

## Is CVE-2020-36632 being exploited?

There is no known exploitation of CVE-2020-36632 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2020-36632 and fix it if it is affected.

What it is: CVE-2020-36632 is a medium-severity vulnerability in hughsk flat, published on 25 Dec 2022. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2020-36632 in the wild and no public exploit code.

Affected packages and fixed versions:
- flat (npm): affected all versions; fixed in 1.6.2
- flat (npm): affected all versions; fixed in 1.6.2
- flat (npm): affected from 2.0.0; fixed in 2.0.2
- flat (npm): affected from 2.0.0; fixed in 2.0.2
- flat (npm): affected from 3.0.0; fixed in 3.0.1
- flat (npm): affected from 3.0.0; fixed in 3.0.1
- flat (npm): affected from 4.0.0; fixed in 4.0.2
- flat (npm): affected from 4.0.0; fixed in 4.0.2
- flat (npm): affected from 5.0.0; fixed in 5.0.1
- flat (npm): affected from 5.0.0; fixed in 5.0.1

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-2020-36632/ (Markdown: https://insights.sbomify.com/CVE-2020-36632/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-36632
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-36632
- OSV: https://osv.dev/vulnerability/CVE-2020-36632

---
From sbomify Insights: https://insights.sbomify.com/CVE-2020-36632/
Summaries are generated and may contain mistakes; the official description above is the record.