CVE-2021-43803

mediumpriority · track · 34EPSS 0.473 · 99 %ileEUUS

grimoire priorityP1 · Urgent

Exploitable?

—

no known exploitation

Likely / severe?

47.3% (99th) EPSS

CVSS 4.3 · medium

Is it mine?

6 products

Check your exposure

Who says so?

4 sources

cnnvd · enisa_euvd · nvd · osv

EPSS · scored 2026-10-27

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.

cvss

Technical severity, 0–10. One row per scoring source.

7.5

010

base score 0–10 · higher = more severe · hover a vector to decode⚠ sources disagree · medium–high · 4.3–7.5

v2.04.3mediumAV:N/AC:M/Au:N/C:N/I:N/A:Pprimary · NVD / NIST USexploitability 8.6 · impact 2.9

v3.17.5highCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:Hsecondary · ENISA EU

v3.17.5highCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:Hsecondary · security-advisories@github.comexploitability 3.9 · impact 3.6

v3.17.5highCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:Hsecondary · OSV

v3.17.5highCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H/E:Hsecondary · CVSS-BT (t0sche)

weaknesses

The CWE weakness classes this flaw belongs to.

CWE-20USCWE-20US

affected products (6)

Products and version ranges known to be affected.

vercel next.js11.1.0, → 11.1.3enisa_euvdEU
vercel next.js12.0.0, → 12.0.5enisa_euvdEU
vercel next.js11.1.0 → 11.1.3nvdUScpe:2.3:a:vercel:next.js:*:*:*:*:*:*:*:*
vercel next.js12.0.0 → 12.0.5nvdUScpe:2.3:a:vercel:next.js:*:*:*:*:*:*:*:*
npm next0.9.9 → 11.1.3osvUSpkg:npm/next
npm next12.0.0 → 12.0.5osvUSpkg:npm/next

advisories (1)

Vendor and ecosystem advisories describing this.

GHSA-25mp-g6fv-mqxxUnexpected server crash in Next.js.2021-12-07ghsa · osvUS
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. Note that prior version 0.9.9 package `next` hosted a different utility (0.4.1 being the latest version of that codebase), and this advisory does not apply to those versions.

also known as (3)

Other names and identifiers for this entity.

sources

Which sources assert this record, and when.

cnnvd enisa_euvd nvd osv NVD CVE.org MITRE

published 2021-12-10modified 2026-06-17

references (15)

External citations — patches, advisories, analysis.

scry

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