CVE-2021-43803

Next.Js vulnerability

CVSS

7.5

EPSS

44.8%

EPSS pct

99th

Exploited

No known

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.

Affected vendor

Vercel

Affected product

Next.Js

CVSS vector

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

Weakness type (CWE)

CWE-20 — Improper Input Validation

Published

2021-12-10

Risk analysis

Based on its CVSS vector, this vulnerability is exploitable over the network, low attack complexity, requiring no privileges, no user interaction. Successful exploitation leads to high impact to availability.

Its EPSS score of 44.8% reflects a moderate probability of exploitation activity in the wild over the next 30 days, placing it among the most exploited CVEs currently tracked.

Check your external exposure to CVE-2021-43803

Confirm whether Vercel Next.Js is running on any internet-facing host or subdomain.
Match discovered service fingerprints against the version affected by CVE-2021-43803.
Prioritise remediation if the asset is public, business-critical, or near authentication/payment flows.

How ThreatPort helps with CVE-2021-43803

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