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CVE-2026-34226

Capricorn86 Happy Dom vulnerability

7.5 HIGHPublic exploitEPSS 0.59%
  1. Published27 Mar 2026

Description

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.

CVSS 3.1 breakdown

Attack vectorNetwork
Attack complexityLow
Privileges requiredNone
User interactionNone
ScopeUnchanged
ConfidentialityHigh
IntegrityNone
AvailabilityNone
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Affected products

Capricorn86 Happy Dom< 20.8.9

Remediation

Fixed in
Capricorn86 Happy Dom≥ 20.8.9

References

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Frequently asked

Is CVE-2026-34226 being actively exploited?

CVE-2026-34226 is not in the CISA KEV catalog. A public exploit reference exists, so treat it as exploitable. Its EPSS exploit probability is 0.59%.

How severe is CVE-2026-34226?

CVE-2026-34226 has a CVSS 3.1 base score of 7.5, rated high. EPSS estimates a 0.59% probability of exploitation.

Which products are affected by CVE-2026-34226?

Affected products include Capricorn86 Happy Dom.

How do I fix CVE-2026-34226?

Upgrade affected software to a fixed version, for example Capricorn86 Happy Dom 20.8.9 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2026-34226 against the real software inventory on every managed device, every day. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

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Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.