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CVE-2021-43803

Unexpected server crash in Next.js

HIGH
7.5
CVSS Score
Published: December 9, 2021 at 11:50 PM UTC
Updated: June 17, 2026 at 04:11 AM UTC
1 product affected across 1 vendorNext.js· also runs on 1 platform

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Severity
HIGH7.5
Exploit prediction
EPSS 47%

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Next.js· Vercelnpm
95%
v < 11.1.3v < 12.0.511.1.0 ≤ v < 11.1.312.0.0 ≤ v < 12.0.5
Affected range stops below 11.1.3, so it looks safe — our inference, not a vendor statement
Affected range stops below 12.0.5, so it looks safe — our inference, not a vendor statement
nodejs-node-js (environment)

Runs on — not affected

The affected product only carries this flaw when running on these platforms. The platforms themselves are not vulnerable.

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

Patch and advisory references

References (5)

x_refsource_MISCPatchThird Party Advisory
Source: [email protected]
https://github.com/vercel/next.js/commit/6d98b4fb4315dec1badecf0e9bdc212a4272b264
x_refsource_MISCPatchThird Party Advisory
Source: [email protected]
https://github.com/vercel/next.js/pull/32080
x_refsource_MISCRelease NotesThird Party Advisory
Source: [email protected]
https://github.com/vercel/next.js/releases/tag/v11.1.3
x_refsource_MISCRelease NotesThird Party Advisory
Source: [email protected]
https://github.com/vercel/next.js/releases/v12.0.5
x_refsource_CONFIRMPatchThird Party Advisory
Source: [email protected]
https://github.com/vercel/next.js/security/advisories/GHSA-25mp-g6fv-mqxx

CVSS

7.5HIGHGitHub_M
Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
NONE
Integrity
NONE
Availability
HIGH
Vector?

Quick Info

StatusMODIFIED
CWE
CWE-20NVD-CWE-noinfo

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