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CVE-2026-34226

HIGH CVSS 3.1: 7.5 EPSS 0.03%
Updated Mar 30, 2026
Happy
Parameter Value
CVSS 7.5 (HIGH)
Affected Versions before 20.8.9
Type CWE-201, CWE-359
Vendor Happy
Public PoC No

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.

Attack Parameters

Attack Vector
Network
Can be exploited remotely
Attack Complexity
Low
Easy to exploit
Privileges Required
None
No privileges needed
User Interaction
None
No user interaction needed

Impact Assessment

Confidentiality
High
Complete data leak
Integrity
None
No data modification
Availability
None
No disruption

CVSS Vector v3.1

Weakness Type (CWE)