CVE-2026-21712
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Assertion Failure in Node.js URL.format() Causes Process Crash

Publication date: 2026-03-30

Last updated on: 2026-05-10

Assigner: HackerOne

Description
A flaw in Node.js URL processing causes an assertion failure in native code when `url.format()` is called with a malformed internationalized domain name (IDN) containing invalid characters, crashing the Node.js process.
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Meta Information
Published
2026-03-30
Last Modified
2026-05-10
Generated
2026-06-16
AI Q&A
2026-03-30
EPSS Evaluated
2026-06-14
NVD
CVE-2026-21712
EUVD
EUVD-2026-17093
Affected Vendors & Products
Showing 3 associated CPEs
Vendor Product Version / Range
nodejs node.js 24.14.1
nodejs node.js 25.8.2
nodejs node.js From 20.0.0 (inc) to 26.0.0 (exc)
Helpful Resources
Exploitability
CWE
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KEV
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CWE ID Description
CWE-20 The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.
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Executive Summary

CVE-2026-21712 is a medium severity vulnerability in Node.js that occurs when the url.format() function is called with a malformed internationalized domain name (IDN) containing invalid characters.

This malformed input causes an assertion failure in the native code (specifically in the file node_url.cc), which leads to the Node.js process crashing.

Impact Analysis

The vulnerability can cause the Node.js process to crash unexpectedly when processing certain malformed URLs.

This crash can lead to denial of service conditions in applications relying on Node.js, potentially disrupting service availability.

Detection Guidance

This vulnerability causes the Node.js process to crash when the `url.format()` function is called with a malformed internationalized domain name (IDN) containing invalid characters.

To detect this vulnerability on your system, you can monitor for unexpected Node.js process crashes or assertion failures related to URL processing.

There are no specific commands provided in the available resources to detect this vulnerability directly.

Mitigation Strategies

The immediate mitigation step is to upgrade Node.js to a fixed version that addresses this vulnerability.

  • Upgrade to Node.js version 24.14.1 or later if you are using the 24.x release line.
  • Upgrade to Node.js version 25.8.2 or later if you are using the 25.x release line.

These versions include the fix for CVE-2026-21712 and prevent the assertion failure caused by malformed IDNs.

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