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
References8
- github.com/capricorn86/happy-dom/security/advisories/GHSA-w4gp-… ExploitVendor Advisory
- github.com/capricorn86/happy-dom/blob/f8d8cad41e9722fab9eefb9df… Patch
- github.com/capricorn86/happy-dom/commit/68324c21d7b98f53f7bb5a7… Patch
- github.com/capricorn86/happy-dom/pull/2117 Issue TrackingPatch
- github.com/capricorn86/happy-dom/releases/tag/v20.8.9 ProductRelease Notes
- access.redhat.com/security/cve/CVE-2026-34226
- bugzilla.redhat.com/show_bug.cgi?id=2452519
- security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-34226…
Metrics
- CVSS 3.1
-
7.5
HIGH
Score source: CNA
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N - EPSS — exploit probability
- 0% percentile: 41 · as of 12 November 2026
- CWE
- CWE-201CWE-359
Could this be exploited in your environment?
A patch closes the known hole. A penetration test shows what an attacker can still reach — with proof.