# CVE-2021-46518: Memory corruption in n/a

> A heap buffer overflow in the MJS JavaScript engine allows attackers to execute arbitrary code or cause a denial of service.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 27 Jan 2022
- **Updated:** 4 Aug 2024
- **Also known as:** GHSA-rrr6-r9v5-phwp

## What is CVE-2021-46518?

CVE-2021-46518 is a high-severity memory corruption vulnerability in Cesanta Mjs, published on 27 Jan 2022. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.

### Official description

Cesanta MJS v2.20.0 was discovered to contain a heap buffer overflow via mjs_disown at src/mjs_core.c.

Weakness: CWE-787 (Out-of-bounds Write)

## Which versions are affected by CVE-2021-46518?

It affects 1 product.


Products: Cesanta Mjs.

## How do I fix CVE-2021-46518?

No fix has been published for CVE-2021-46518 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-46518 being exploited?

There is no known exploitation of CVE-2021-46518 in the wild and no public exploit code.

## Other vulnerabilities in Cesanta Mjs

- [CVE-2023-50044](https://insights.sbomify.com/CVE-2023-50044/): Memory corruption in n/a (critical 9.8)
- [CVE-2023-43338](https://insights.sbomify.com/CVE-2023-43338/): Memory corruption in n/a (critical 9.8)
- [CVE-2021-46509](https://insights.sbomify.com/CVE-2021-46509/): Denial of service in n/a (high 7.8)
- [CVE-2021-46513](https://insights.sbomify.com/CVE-2021-46513/): Memory corruption in n/a (high 7.8)
- [CVE-2021-46519](https://insights.sbomify.com/CVE-2021-46519/): Memory corruption in n/a (high 7.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-46518 and fix it if it is affected.

What it is: CVE-2021-46518 is a high-severity memory corruption vulnerability in Cesanta Mjs, published on 27 Jan 2022. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2021-46518 in the wild and no public exploit code.

Affected product: Cesanta Mjs. No package-level version data is available, so check the vendor advisory linked from the reference page.

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-2021-46518/ (Markdown: https://insights.sbomify.com/CVE-2021-46518/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-46518
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-46518
- OSV: https://osv.dev/vulnerability/CVE-2021-46518

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-46518/
Summaries are generated and may contain mistakes; the official description above is the record.