CVE-2026-34226 Happy DOM's fetch credentials include uses page-origin cookies instead of target-origin cookies
Happy DOM leaks cookies from the current page origin to the target URL during fetch requests, exposing sensitive session data.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-34226?
CVE-2026-34226 is a high-severity vulnerability in capricorn86 happy-dom, published on 27 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
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.
Which versions are affected by CVE-2026-34226?
2 open source packages ship an affected version, including happy-dom. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
happy-dom npm | All versions | 20.8.9 |
happy-dom npm | All versions | 20.8.9 |
Products include Capricorn86 Happy Dom.
How do I fix CVE-2026-34226?
Upgrade happy-dom to 20.8.9 or later.
Is CVE-2026-34226 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-34226 exists.
Other vulnerabilities in capricorn86 happy-dom
Sources
Also known as CLSA-2026-1790598377, CLSA-2026-1792191308, CLSA-2026-1792254633, CLSA-2026-1792254634, CLSA-2026-1792866974, CLSA-2026-1792866976 and 1 more.