Insertion of Sensitive Information Into Sent Data in Happy DOM - CVE-2026-34226
Published: April 27, 2026
Vulnerability identifier: #VU128058
CSH Severity: Medium
CVSS v4: 8.7 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-34226
CWE-ID: CWE-201
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to disclose sensitive information.
The vulnerability exists due to insertion of sensitive information into sent data in getRequestHeaders() in packages/happy-dom/src/fetch/utilities/FetchRequestHeaderUtility.ts when processing fetch requests with credentials set to include. A remote attacker can trigger a cross-origin request to cause cookies from the current page origin to be sent to the request destination.
This issue affects authenticated or session-based flows that rely on browser-like fetch behavior across different origins.
Affected software
Happy DOM
How to mitigate CVE-2026-34226
Install security update from vendor's website.
Happy DOM - update to 20.8.9