CVE-2026-21712: A flaw in Node.js URL processing causes an assertion failure in native code when `url.format()` is called with

Routine

MEDIUM 6.5UPGRADE

CVE-2026-21712 is a medium-severity flaw (CVSS 6.5) affecting node.js. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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.

Why this priority

No elevated risk signals yet

A fixed release or distro patch exists.

Risk facts

CVSS score	6.5 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	0.3% (top 74%)
CISA exploited list	No
Weakness	CWE-20
Published	2026-03-30
Last modified	2026-08-19

Publisher (CNA): HackerOne · Vendor: nodejs

Last updated 2026-08-19 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-03-30 16:16 UTCPublished CVE record published
2026-08-19 14:05 UTCUpdated Record last modified

nodejs node.js UPGRADE

Affected: >= 24.0.0 and <= 24.14.0 · >= 25.0.0 and <= 25.8.1

Fixed in: newer than 25.8.1

Safe to downgrade to: a release before 24.0.0

1. Check installed version

apt-cache policy node.js || rpm -q node.js || node.js --version

2. UPGRADE to newer than 25.8.1 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade node.js

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade node.js

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 24.0.0 (Debian / Ubuntu)

apt-cache madison node.js sudo apt install node.js=<VERSION_BEFORE_24.0.0> sudo apt-mark hold node.js

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list node.js sudo dnf downgrade node.js-<VERSION_BEFORE_24.0.0> sudo dnf versionlock add node.js

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-21712?

node.js: upgrade to newer than 25.8.1. Exact commands for each OS are on this page.

Is CVE-2026-21712 being exploited?

CVE-2026-21712 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-21712 affect?

CVE-2026-21712 affects node.js. Severity is medium (CVSS 6.5). 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.

How urgent is CVE-2026-21712?

Priority 29/100. No elevated risk signals yet.

Software pages

Node.js vulnerabilities

Related CVEs

CVE-2026-48617 HIGH 8.2 UPGRADE A flaw in Node.js Permission Model enforcement allows Bypass via `process.report.writeReport()` Path Misvalida
CVE-2026-48937 HIGH 7.5 UPGRADE A flaw in Node.js HTTP/2 server API can cause servers to keep accepting data even after sending a `GOAWAY` fra
CVE-2026-48931 LOW 3.7 DOWNGRADE A flaw in Node.js HTTP Agent can cause a client to accept as valid a response that is send before the client h
CVE-2026-48933 HIGH 7.5 DOWNGRADE A flaw in Node.js WebCrypto implementation can crash the process if the input of `subtle.encrypt()` is a multi
CVE-2026-48618 MEDIUM 6.5 DOWNGRADE A flaw in Node.js TLS hostname handling can cause Node.js unicode dot separator handling can lead to tls wildc

References

← Back to latest CVEs