What’s Vulnerable › Vulnerabilities

CVE-2026-34226: Happy DOM's fetch credentials include uses page-origin cookies instead of target-origin cookies

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.5% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2026-03-27 · updated 2026-10-26
• Weakness: CWE-201

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.

Affected products

• capricorn86 happy-dom: before 20.8.9 — fixed in 20.8.9

How to fix

Upgrade to a fixed version: capricorn86 happy-dom 20.8.9. Check the vendor advisory for mitigations.

References

• https://github.com/capricorn86/happy-dom/blob/f8d8cad41e9722fab9eefb9dfb3cca696462e908/packages/happy-dom/src/fetch/utilities/FetchRequestHeaderUtility.ts
• https://github.com/capricorn86/happy-dom/commit/68324c21d7b98f53f7bb5a7b3e185bda7106e751
• https://github.com/capricorn86/happy-dom/pull/2117
• https://github.com/capricorn86/happy-dom/releases/tag/v20.8.9
• https://github.com/capricorn86/happy-dom/security/advisories/GHSA-w4gp-fjgq-3q4g
• https://access.redhat.com/security/cve/CVE-2026-34226
• https://bugzilla.redhat.com/show_bug.cgi?id=2452519
• https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-34226.json

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