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Fencer Vulns
high 7.5

CVE-2026-34226 json

Happy DOM's fetch credentials include uses page-origin cookies instead of target-origin cookies

published 2026-03-27 7 mo ago modified 2026-10-26 13 d ago also GHSA-w4gp-fjgq-3q4g , EUVD-2026-16893

cvss
7.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.5%
EPSS 0.5% chance of exploitation in 30 days, percentile 40%
public exploits
0
none known

Summary

Happy DOM is a JavaScript implementation of a web browser without its graphical user interface. Versions prior to 20.8.9 may attach cookies from the current page origin (`window.location`) instead of the request target URL when `fetch(..., { credentials: "include" })` is used. This can leak cookies from origin A to destination B. Version 20.8.9 fixes the issue.

Patch / fix

  • npm happy-dom 20.8.9
  • capricorn86 happy_dom 20.8.9

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-34226 updated cvss 7.5

happy-dom: Happy DOM: Information disclosure via incorrect cookie handling in fetch requests

  • Red Hat Ansible Automation Platform 2 ansible-automation-platform-26/gateway-rhel9
    affected: no fix planned “Will not fix”
  • Red Hat OpenShift Container Platform 4 openshift4/ose-agent-installer-ui-rhel9
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
Proof of concept is public
Automatable
yes
Technical impact
partial
Assessed
7 mo ago

Exploit prediction

0.47% chance of exploitation in the next 30 days, higher than 40% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/capricorn86/happy-dom/security/advisories/GHSA-w4gp-fjgq-3q4g referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
CISA ADP 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
GitHub 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Affected packages

ecosystem package affected fixed in
npm happy-dom
<20.8.9
20.8.9

Affected products

  • capricorn86 happy-dom
  • Red Hat Red Hat Ansible Automation Platform 2
  • Red Hat Red Hat OpenShift Container Platform 4

Classification

Weakness
  • CWE-201 Insertion of Sensitive Information Into Sent Data
  • CWE-359 Exposure of Private Personal Information to an Unauthorized Actor

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.