CVE-2026-21710: A flaw in Node.js HTTP request handling causes an uncaught `TypeError` when a request is received with a heade

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HIGH 7.5REMOTEWATCHLISTUPGRADEMITIGATEMITIGATE

CVE-2026-21710 is a high-severity flaw (CVSS 7.5) affecting node.js, enterprise linux, enterprise linux eus. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

A flaw in Node.js HTTP request handling causes an uncaught `TypeError` when a request is received with a header named `__proto__` and the application accesses `req.headersDistinct`. When this occurs, `dest["__proto__"]` resolves to `Object.prototype` rather than `undefined`, causing `.push()` to be called on a non-array. This exception is thrown synchronously inside a property getter and cannot be intercepted by `error` event listeners, meanin

Why this priority

High severity
EPSS top 2%: very likely to be exploited
Remotely exploitable, no login, no user action
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	25.4% (top 2%)
CISA exploited list	No
Weakness	CWE-770, CWE-843
Published	2026-03-30
Last modified	2026-08-19

Publisher (CNA): HackerOne · Vendor: nodejs · redhat

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 20:16 UTCPublished CVE record published
2026-08-19 14:32 UTCUpdated Record last modified

nodejs node.js UPGRADE

Affected: <= 20.20.1 · >= 22.0.0 and <= 22.22.1 · >= 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 22.0.0

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 22.0.0 (Debian / Ubuntu)

apt-cache madison node.js sudo apt install node.js=<VERSION_BEFORE_22.0.0> 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_22.0.0> 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.

redhat enterprise linux MITIGATE

Affected: 8.0 · 9.0 · 10.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 8.0

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

redhat enterprise linux eus MITIGATE

Affected: 9.4 · 9.6 · 10.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 9.4

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

Exact fixes by distribution

A distro patch exists: prefer upgrading over downgrading.

Fedora ELN · perl-Encode · FIXED · 3.25-528.eln159 · FEDORA-2026-79991d0238 · source

sudo dnf upgrade --advisory=FEDORA-2026-79991d0238

Fedora 46 · fonttools · FIXED · 4.68.0-1.fc46 · FEDORA-2026-65d6c01c75 · source

sudo dnf upgrade --advisory=FEDORA-2026-65d6c01c75

Debian 12 · nodejs · FIXED · 18.20.4+dfsg-1~deb12u2

sudo apt update && sudo apt install --only-upgrade nodejs dpkg --compare-versions "$(dpkg-query -W -f='${Version}' nodejs)" ge "18.20.4+dfsg-1~deb12u2" && echo PATCHED || echo STILL-VULNERABLE

Debian 13 · nodejs · FIXED · 20.19.2+dfsg-1+deb13u2

sudo apt update && sudo apt install --only-upgrade nodejs dpkg --compare-versions "$(dpkg-query -W -f='${Version}' nodejs)" ge "20.19.2+dfsg-1+deb13u2" && echo PATCHED || echo STILL-VULNERABLE

RHEL 10 · nodejs22 · FIXED · nodejs22-22.22.2-1.el10_1

sudo dnf upgrade --advisory=RHSA-2026:7080 rpm -q nodejs22

RHEL 10 · nodejs24 · FIXED · nodejs24-24.14.1-2.el10_1

sudo dnf upgrade --advisory=RHSA-2026:7675 rpm -q nodejs24

RHEL 10.0 Extended Update Support · nodejs22 · FIXED · nodejs22-22.22.2-2.el10_0

sudo dnf upgrade --advisory=RHSA-2026:7310 rpm -q nodejs22

Alpine 3.21 · nodejs · FIXED · nodejs-22.22.2-r0

apk add --upgrade nodejs apk info -v nodejs

Alpine 3.22 · nodejs · FIXED · nodejs-22.22.2-r0

apk add --upgrade nodejs apk info -v nodejs

Alpine 3.23 · nodejs · FIXED · nodejs-24.14.1-r0

apk add --upgrade nodejs apk info -v nodejs

Alpine 3.24 · nodejs · FIXED · nodejs-24.14.1-r0

apk add --upgrade nodejs apk info -v nodejs

Amazon Linux 2023 · see advisory · FIXED · ALAS2023-2026-1578 · source

sudo dnf update --advisory=ALAS2023-2026-1578

Public exploits and detection

Public code exists for this CVE. Treat unpatched systems as at risk, and only run PoCs in a lab.

GitHub PoC: open-flaw/CVE-2026-21710 (0 stars)

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-2026-21710?

node.js: upgrade to newer than 25.8.1; enterprise linux: mitigate or apply the listed mitigation; enterprise linux eus: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2026-21710 being exploited?

CVE-2026-21710 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-2026-21710 affect?

CVE-2026-21710 affects node.js, enterprise linux, enterprise linux eus. Severity is high (CVSS 7.5). A flaw in Node.js HTTP request handling causes an uncaught `TypeError` when a request is received with a header named `__proto__` and the application accesses `req.headersDistinct`. When this occurs, `dest["__proto__"]` resolves to `Obje

How urgent is CVE-2026-21710?

Priority 61/100. High severity; EPSS top 2%: very likely to be exploited; Remotely exploitable, no login, no user action; On your watchlist

Software pages

Node.js vulnerabilities

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References

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