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CVE-2021-43803

49
FAUCET Score

CVE-2021-43803 describes a server crash vulnerability in Next.js versions 11.1.0 through 12.0.4 when deployed with Node.js 15.0.0+ using next start or a custom server. This high-severity vulnerability (CVSS 7.5) allows an unauthenticated attacker to cause a denial of service by sending invalid or malformed URLs. While no public exploits or active exploitation have been observed, and community discussion is minimal, affected organizations should prioritize upgrading to Next.js 12.0.5 or 11.1.3 to mitigate this risk.

Impacted Technologies

VendorProductVersion(s)CPE
>= 11.1.0, < 11.1.3CPE matchmatch criteria
cpe:2.3:a:vercel:next.js:*:*:*:*:*:node.js:*:*
>= 12.0.0, < 12.0.5CPE matchmatch criteria
cpe:2.3:a:vercel:next.js:*:*:*:*:*:node.js:*:*

CVSS Data

CVSS version used by this source: 3.1

7.5HIGH

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

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
NONE
Availability Impact
HIGH
Exploitability Score
3.9
Impact Score
3.6
CvssVersion
3.1

Exploit Intelligence

EPSS Score
44.82%
Probability of exploitation in next 30 days
EPSS Percentile
98.6%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.4482 is in the 98th percentile among its peer group of 51,506 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.1 Mastodon, and 0.4 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (3)

github_advisorypatch availablevia nvd_reference
View patch
npmpatch availablevia ghsa
Product: nextFixed in: 12.0.5
npmpatch availablevia ghsa
Product: nextFixed in: 11.1.3

Vendor Advisories (1)

npmGHSA-25mp-g6fv-mqxxhigh

Unexpected server crash in Next.js.

Dec 7, 2021

References

github.com / vercel/next.js/commit/6d98b4fb4315dec1badecf0e9bdc212a4272b264
PatchThird Party Advisory
github.com / vercel/next.js/pull/32080
PatchThird Party Advisory
github.com / vercel/next.js/releases/tag/v11.1.3
Release NotesThird Party Advisory
github.com / vercel/next.js/releases/v12.0.5
Release NotesThird Party Advisory
github.com / vercel/next.js/security/advisories/GHSA-25mp-g6fv-mqxx
PatchThird Party Advisory