Vulnerability in Capricorn86 Happy-Dom
CVE-2026-34226
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.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N.
EPSS exploit prediction
EPSS: 0.006 (46.0th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 46th percentile — 46.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.005 · newest: 0.006 · change: +0.001
Affected products
- Capricorn86 Happy-Dom — versions < 20.8.9
- Capricorn86 Happy Dom
Weakness classification (CWE)
References
- github.com/capricorn86/happy-dom/security/advisories/GHSA-w4gp-fjgq-3q4g (Exploit, Vendor Advisory)
- github.com/capricorn86/happy-dom/pull/2117 (Patch, Issue Tracking)
- github.com/capricorn86/happy-dom/commit/68324c21d7b98f53f7bb5a7b3e185bda7106e751 (Patch)
- github.com/capricorn86/happy-dom/blob/f8d8cad41e9722fab9eefb9dfb3cca696462e908/… (Patch)
- github.com/capricorn86/happy-dom/releases/tag/v20.8.9 (Product, Release Notes)
- 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
- 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
- 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
Frequently asked questions
- What is CVE-2026-34226?
- CVE-2026-34226 is a high-severity vulnerability in Capricorn86 Happy-Dom, classified under Insertion of Sensitive Information into Sent Data. CVSS score: 7.5/10. Published 2026-03-27.
- How severe is CVE-2026-34226?
- High severity. CVSS v3 base score is 7.5 out of 10.