CVE-2021-43803

Name: CVE-2021-43803
Creator: NVD / NIST
Published: 2021-12-10T00:15:11.827+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

HIGHCVSS 7.5/10EPSS 44.82%

Last modified Jun 17, 2026

CVE-2021-43803 is a high-severity vulnerability rated 7.5/10 on the CVSS scale. Next.js is a React framework. In versions of Next.js prior to 12.0.5 or 11.1.3, invalid or malformed URLs could lead to a server crash. EPSS estimates a 44.82% chance of exploitation in the next 30 days.

Description

Next.js is a React framework. In versions of Next.js prior to 12.0.5 or 11.1.3, invalid or malformed URLs could lead to a server crash. In order to be affected by this issue, the deployment must use Next.js versions above 11.1.0 and below 12.0.5, Node.js above 15.0.0, and next start or a custom server. Deployments on Vercel are not affected, along with similar environments where invalid requests are filtered before reaching Next.js. Versions 12.0.5 and 11.1.3 contain patches for this issue.

Metrics

CVSS 3.1

7.5/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS Probability

44.82%

98.6th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-20

Affected Software

Vendor	Product	Versions
Vercel	Next.Js	>= 11.1.0, < 11.1.3
Vercel	Next.Js	>= 12.0.0, < 12.0.5

References

https://github.com/vercel/next.js/commit/6d98b4fb4315dec1badecf0e9bdc212a4272b264Patch, Third Party Advisory
https://github.com/vercel/next.js/pull/32080Patch, Third Party Advisory
https://github.com/vercel/next.js/releases/tag/v11.1.3Release Notes, Third Party Advisory
https://github.com/vercel/next.js/releases/v12.0.5Release Notes, Third Party Advisory
https://github.com/vercel/next.js/security/advisories/GHSA-25mp-g6fv-mqxxPatch, Third Party Advisory
https://github.com/vercel/next.js/commit/6d98b4fb4315dec1badecf0e9bdc212a4272b264Patch, Third Party Advisory
https://github.com/vercel/next.js/pull/32080Patch, Third Party Advisory
https://github.com/vercel/next.js/releases/tag/v11.1.3Release Notes, Third Party Advisory
https://github.com/vercel/next.js/releases/v12.0.5Release Notes, Third Party Advisory
https://github.com/vercel/next.js/security/advisories/GHSA-25mp-g6fv-mqxxPatch, Third Party Advisory

Timeline

Published: Dec 10, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-43803?

How severe is CVE-2021-43803?

CVE-2021-43803 has a CVSS score of 7.5/10 (HIGH severity). The EPSS model estimates a 44.82% probability of exploitation in the next 30 days.

How do I fix CVE-2021-43803?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-43803?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST