# CVE-2021-39227: Fix prototype pollution in the zrender merge and clone helper methods

> Prototype pollution in ZRender's merge and clone methods allows attackers to manipulate object prototypes, potentially leading to code execution or privilege escalation.

- **Severity:** Medium 6.2 (`CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 17 Sep 2021
- **Updated:** 4 Aug 2024
- **Also known as:** GHSA-fhv8-fx5f-7fxf

## What is CVE-2021-39227?

CVE-2021-39227 is a medium-severity vulnerability in ecomfe zrender, published on 17 Sep 2021. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

ZRender is a lightweight graphic library providing 2d draw for Apache ECharts. In versions prior to 5.2.1, using `merge` and `clone` helper methods in the `src/core/util.ts` module results in prototype pollution. It affects the popular data visualization library Apache ECharts, which uses and exports these two methods directly. The GitHub Security Advisory page for this vulnerability contains a proof of concept. This issue is patched in ZRender version 5.2.1. One workaround is available: Check if there is `__proto__` in the object keys. Omit it before using it as an parameter in these affected methods. Or in `echarts.util.merge` and `setOption` if project is using ECharts.

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

## Which versions are affected by CVE-2021-39227?

4 open source packages ship an affected version, including zrender. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `zrender` | npm | All versions | 4.3.3 |
| `zrender` | npm | All versions | 4.3.3 |
| `zrender` | npm | From 5.0.0 | 5.2.1 |
| `zrender` | npm | From 5.0.0 | 5.2.1 |

Products: Baidu Zrender.

## How do I fix CVE-2021-39227?

Upgrade zrender to a fixed version for your release line: 4.3.3 or 5.2.1.

## Is CVE-2021-39227 being exploited?

There is no known exploitation of CVE-2021-39227 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-39227 and fix it if it is affected.

What it is: CVE-2021-39227 is a medium-severity vulnerability in ecomfe zrender, published on 17 Sep 2021. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-39227 in the wild and no public exploit code.

Affected packages and fixed versions:
- zrender (npm): affected all versions; fixed in 4.3.3
- zrender (npm): affected all versions; fixed in 4.3.3
- zrender (npm): affected from 5.0.0; fixed in 5.2.1
- zrender (npm): affected from 5.0.0; fixed in 5.2.1

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-2021-39227/ (Markdown: https://insights.sbomify.com/CVE-2021-39227/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-39227
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-39227
- OSV: https://osv.dev/vulnerability/CVE-2021-39227

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From sbomify Insights: https://insights.sbomify.com/CVE-2021-39227/
Summaries are generated and may contain mistakes; the official description above is the record.