# CVE-2023-30421: Denial of service in mjson

> An attacker can cause a denial of service in the mjson library by providing specific digit strings that trigger excessive processing iterations.

- **Severity:** Low 2.9 (`CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 19 Apr 2025
- **Updated:** 21 Apr 2025
- **Also known as:** GHSA-rqfj-9wmv-vpgp

## What is CVE-2023-30421?

CVE-2023-30421 is a low-severity denial of service vulnerability in mjson, published on 19 Apr 2025. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

mystrtod in mjson 1.2.7 requires more than a billion iterations during processing of certain digit strings such as 8891110122900e913013935755114.

Weakness: CWE-407 (Inefficient Algorithmic Complexity)

## Which versions are affected by CVE-2023-30421?


## How do I fix CVE-2023-30421?

No fix has been published for CVE-2023-30421 yet. Limit exposure of the affected software until one is available.

## Is CVE-2023-30421 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2023-30421 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2023-30421 and fix it if it is affected.

What it is: CVE-2023-30421 is a low-severity denial of service vulnerability in mjson, published on 19 Apr 2025. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2023-30421 exists.

Affected product: mjson. 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-2023-30421/ (Markdown: https://insights.sbomify.com/CVE-2023-30421/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-30421
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-30421
- OSV: https://osv.dev/vulnerability/CVE-2023-30421

---
From sbomify Insights: https://insights.sbomify.com/CVE-2023-30421/
Summaries are generated and may contain mistakes; the official description above is the record.