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Public proof of conceptFix available

CVE-2026-21710

A public proof of concept exists; no exploitation attested.

  • Published2026-03-30
  • WeaknessCWE-770 · CWE-843

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

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, meaning it cannot be handled without wrapping every `req.headersDistinct` access in a `try/catch`. * This vulnerability affects all Node.js HTTP servers on **20.x, 22.x, 24.x, and v25.x**

Timeline

dates in UTC
  1. 2026-03-3020:16CVE publishedNVD
  2. 2026-10-2319:23First public proof of conceptPoC-in-GitHub
  3. 2026-10-2319:23EPSS crossed 10 %FIRST EPSS

Observed activity

isMalicious corpus · updated 2026-10-23 18:48 UTC
Indicators tagged with this CVE, per day0 indicators over 7 days
Block these indicators
  • Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2026-21710?format=txt
  • CSV export: https://api.ismalicious.com/edl/cve/CVE-2026-21710?format=csv
  • TAXII collection of exploited CVEs
  • The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD
Node.js
BranchAffectedFixed in
20.20≤ 20.20.1no fix published
22.x≥ 22.0.0, ≤ 22.22.1no fix published
24.x≥ 24.0.0, ≤ 24.14.0no fix published
25.x≥ 25.0.0, ≤ 25.8.1no fix published
Redhat enterprise linux
BranchAffectedFixed in
8.0= 8.0no fix published
9.0= 9.0no fix published
10.0= 10.0no fix published
Redhat enterprise linux eus
BranchAffectedFixed in
9.4= 9.4no fix published
9.6= 9.6no fix published
10.0= 10.0no fix published

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Distribution builds and vendor advisories

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Vendor advisories

  • RHSA-2026:9874 Red Hat Product Security31 products fixed

    Red Hat Security Advisory: nodejs:20 security update

  • RHSA-2026:9711 Red Hat Product Security31 products fixed

    Red Hat Security Advisory: nodejs:20 security update

  • RHSA-2026:8339 Red Hat Product Security31 products fixed

    Red Hat Security Advisory: nodejs:20 security update

  • RHSA-2026:7983 Red Hat Product Security43 products fixed

    Red Hat Security Advisory: nodejs:22 security update

  • RHSA-2026:7896 Red Hat Product Security31 products fixed

    Red Hat Security Advisory: nodejs:20 security update

  • RHSA-2026:7670 Red Hat Product Security40 products fixed

    Red Hat Security Advisory: nodejs:24 security update

6 more advisories

Full record on NVD

Fix

  1. Vendor fix Red Hat Product Security RHSA-2026:9874 · 31 productsFor details on how to apply this update, which includes the changes described in this advisory, refer to: https://access.redhat.com/articles/11258
  2. Workaround from the vendor Red Hat Product Security RHSA-2026:9874 · 31 productsMitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.

Advisories and patches

Detection

read 2026-10-23 19:25 UTC
Nuclei template
none so far
ProjectDiscovery
Exploit-DB
no entry
Exploit-DB
Proof-of-concept repositories
1 repository, unverifiedopen-flaw/CVE-2026-21710
PoC-in-GitHub

Sources

  • NVDCVE recordread 2026-10-23
  • CISA-ADPSSVC decisionnone2026-03-31
  • OpenCVESSVC decisionnone—
  • CNACVSS 3.17.5read 2026-10-23
  • CNACVSS 3.07.5read 2026-10-23
  • CISA-ADPweakness (CWE)CWE-7702026-03-31
  • CNAweakness (CWE)CWE-843read 2026-10-23
  • FIRST EPSSEPSS score25.0 %read 2026-10-23
  • PoC-in-GitHubproof of concept1read 2026-10-23

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Published
2026-03-30
Last Modified
2026-08-19
NVD status
Analyzed

Frequently asked questions

What is CVE-2026-21710?

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, meaning it cannot be handled without wrapping every `req.headersDistinct` access in a `try/catch`. * This vulnerability affects all Node.js HTTP servers on **20.x, 22.x, 24.x, and v25.x**

Is CVE-2026-21710 actively exploited?

Active exploitation of CVE-2026-21710 has not been confirmed. Its EPSS score was 25.0% on 2026-10-22, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2026-21710?

CVE-2026-21710 has a CVSS v3 base score of 7.5 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

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