# CVE-2021-25945: Prototype pollution vulnerability in js-extend

> Prototype pollution in js-extend allows attackers to cause denial of service and potentially execute remote code.

- **Severity:** Critical 9.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 26 May 2021
- **Updated:** 3 Aug 2024
- **Also known as:** GHSA-mh82-55cm-6gfh

## What is CVE-2021-25945?

CVE-2021-25945 is a critical code injection vulnerability in js-extend, published on 26 May 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Prototype pollution vulnerability in 'js-extend' versions 0.0.1 through 1.0.1 allows attacker to cause a denial of service and may lead to remote code execution.

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

## Which versions are affected by CVE-2021-25945?

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


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `js-extend` | npm | All versions to 1.0.1 | None |
| `js-extend` | npm | All versions to 1.0.1 | None |

Products: Js-Extend Project Js-Extend.

## How do I fix CVE-2021-25945?

No fix has been published for CVE-2021-25945 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-25945 being exploited?

There is no known exploitation of CVE-2021-25945 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-25945 and fix it if it is affected.

What it is: CVE-2021-25945 is a critical code injection vulnerability in js-extend, published on 26 May 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-2021-25945 in the wild and no public exploit code.

Affected packages and fixed versions:
- js-extend (npm): affected all versions up to 1.0.1; no fix listed
- js-extend (npm): affected all versions up to 1.0.1; 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-2021-25945/ (Markdown: https://insights.sbomify.com/CVE-2021-25945/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-25945
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-25945
- OSV: https://osv.dev/vulnerability/CVE-2021-25945

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-25945/
Summaries are generated and may contain mistakes; the official description above is the record.