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Vulnerability · Published Mar 27, 2026 · Assigned by GitHub_M

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

High 7.5

In plain English

A high-severity security flaw in happy-dom from capricorn86. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 41% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)7.5High
Exploit odds (30 days)0.5%top 59.5% of all CVEs
Exploited in the wildNo reportsCISA SSVC: poc
Attack toolingNoneno public tooling known

Official 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 packages & fixed versions

EcosystemPackageFixed inAdvisory
npmhappy-dom20.8.9GHSA-w4gp-fjgq-3q4g

Affected products (as reported)

VendorProductVersions
capricorn86 happy-dom < 20.8.9

Weakness: CWE-201, CWE-359 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

References