Denial of Service Vulnerability in next.js

Answer in brief

CVE-2022-21721 records a Medium severity (CVSS 5.9) vulnerability in Denial of Service Vulnerability in next.js. The current sources do not mark it as known exploited. The current feed maps next (npm). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Jan 28, 2022Updated Sep 10, 2026Source checked Sep 10, 2026First seen by HOL Sep 10, 2026Material review Sep 10, 2026

Upstream Advisory

Key facts

Risk: Medium · CVSS 5.9
Exploitation: Not marked as known exploited
Affected software: 1 mapped package or product
Fix availability: Available

Why this deserves its current priority

CVSS is 5.9. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps next (npm). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
nextnpm	>=12.0.0 <12.0.9	12.0.9

Recommended response

Check inventory. Check lockfiles and deployed manifests for next.
Review the reported fix. Update next to 12.0.9 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Jan 28, 2022
Evidence: source:osv:source_dates:source-dates:record
Source modified
Sep 10, 2026
Evidence: source:osv:source_dates:source-dates:record
First seen by HOL
Sep 10, 2026

Sources and claim methodology

Upstream source description

### Impact Vulnerable code could allow a bad actor to trigger a denial of service attack for anyone running a Next.js app at version >= 12.0.0, and using i18n functionality. - **Affected:** All of the following must be true to be affected by this CVE - Next.js versions above v12.0.0 - Using next start or a custom server - Using the built-in i18n support - **Not affected:** - Deployments on Vercel (vercel.com) are not affected along with similar environments where invalid requests are filtered before reaching Next.js. ### Patches A patch has been released, `[email protected]`, that mitigates this issue. We recommend all affected users upgrade as soon as possible. ### Workarounds We recommend upgrading whether you can reproduce or not although you can ensure `/${locale}/_next/` is blocked from reaching the Next.js instance until you upgrade. ### For more information If you have any questions or comments about this advisory: * Open an issue in [next](https://github.com/vercel/next.js) * Email us at [[email protected]](mailto:[email protected])

Quoted source text, attributed separately from HOL analysis.