# CVE-2021-23421: Prototype Pollution

> Prototype pollution in merge-change allows attackers to modify object prototypes, potentially leading to code execution or privilege escalation.

- **Severity:** Medium 5.6 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L/E:U/RL:U/RC:R`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 11 Aug 2021
- **Updated:** 17 Sep 2024
- **Also known as:** GHSA-f9cv-665r-275h

## What is CVE-2021-23421?

CVE-2021-23421 is a medium-severity vulnerability in merge-change, published on 11 Aug 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

All versions of package merge-change are vulnerable to Prototype Pollution via the utils.set function.

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

## Which versions are affected by CVE-2021-23421?

2 open source packages ship an affected version, including merge-change. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `merge-change` | npm | All versions to 1.8.1 | None |
| `merge-change` | npm | All versions to 1.8.1 | None |

Products: Merge-Change Project Merge-Change.

## How do I fix CVE-2021-23421?

No fix has been published for CVE-2021-23421 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-23421 being exploited?

There is no known exploitation of CVE-2021-23421 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-23421 and fix it if it is affected.

What it is: CVE-2021-23421 is a medium-severity vulnerability in merge-change, published on 11 Aug 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-23421 in the wild and no public exploit code.

Affected packages and fixed versions:
- merge-change (npm): affected all versions up to 1.8.1; no fix listed
- merge-change (npm): affected all versions up to 1.8.1; no fix listed

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-2021-23421/ (Markdown: https://insights.sbomify.com/CVE-2021-23421/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-23421
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-23421
- OSV: https://osv.dev/vulnerability/CVE-2021-23421

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-23421/
Summaries are generated and may contain mistakes; the official description above is the record.