How severe is CVE-2026-34226?

CVE-2026-34226 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity none, and availability none.

Is CVE-2026-34226 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (37th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-34226?

CVE-2026-34226 affects Capricorn86 Happy Dom. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-34226?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

Does CVE-2026-34226 have an EU (EUVD) identifier?

Yes. CVE-2026-34226 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-16893.

When was CVE-2026-34226 published?

CVE-2026-34226 was published on 2026-03-27 and last updated on 2026-06-30.

CVE-2026-34226

CVE-2026-34226 is a high-severity vulnerability in Capricorn86 Happy Dom with a CVSS 3.x base score of 7.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-201.

Key facts

Severity: High (CVSS 3.x base score 7.5)
EPSS exploit prediction: 0% (37th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-16893
Weakness: CWE-201
Affected product: Capricorn86 Happy Dom
Published: 2026-03-27
Last modified: 2026-06-30

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.

Frequently asked questions

What is CVE-2026-34226?: 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.
How severe is CVE-2026-34226?: CVE-2026-34226 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity none, and availability none.
Is CVE-2026-34226 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (37th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-34226?: CVE-2026-34226 affects Capricorn86 Happy Dom. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-34226?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
Does CVE-2026-34226 have an EU (EUVD) identifier?: Yes. CVE-2026-34226 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-16893.
When was CVE-2026-34226 published?: CVE-2026-34226 was published on 2026-03-27 and last updated on 2026-06-30.

References

Affected products (1)

cpe:2.3:a:capricorn86:happy_dom:*:*:*:*:*:nodejs:*:*

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