Happy DOM's fetch credentials include uses page-origin cookies instead of target-origin cookies

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

7.5 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

EPSS

• CVE-2026-34226: 0.47% estimated exploitation activity in the next 30 days; percentile 40.39 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary happy-dom 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. Details In packages/happy-dom/src/fetch/utilities/FetchRequestHeaderUtility.ts (getRequestHeaders()), cookie selection is performed with originURL: Here, originURL represents the page URL, not the request destination URL. For outgoing requests, cookie lookup should use the request URL (for example: new URL(options.request[PropertySymbol.url])). PoC Script Content Environment: 1. Node.js = 22 2. happy-dom 20.6.1 3. DNS names resolving to local loopback via .127.0.0.1.nip.io Reproduction steps: 1. Set page host cookie: pagecookie=PAGEONLY on a.127.0.0.1.nip.io 2. Set target host cookie: apicookie=APIONLY on b.127.0.0.1.nip.io 3. From page host, call fetch to target host with credentials: "include" 4. Observe Cookie header received by the target host Expected: 1.…

Published by the source

29 Mar 2026, 15:23 UTC

Last modified by the source

29 Mar 2026, 15:41 UTC

Source last checked

26 Oct 2026, 12:47 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-w4gp-fjgq-3q4g

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-w4gp-fjgq-3q4g

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# Patch Next advisory brief: CVE-2026-34226

Advisory: Happy DOM's fetch credentials include uses page-origin cookies instead of target-origin cookies
IDs: CVE-2026-34226, GHSA-w4gp-fjgq-3q4g
Record: https://patchnext.com/advisories/cve-2026-34226 (revision 2, source checked 26 Oct 2026, 12:47 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: happy-dom 20.8.9. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm happy-dom: affected < 20.8.9; fixed in 20.8.9

## Suggested inspection (read-only)
- `npm ls happy-dom --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on happy-dom.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-w4gp-fjgq-3q4g (OSV record GHSA-w4gp-fjgq-3q4g lists affected ranges: npm happy-dom >=0 <20.8.9 (fixed))
- Verified: https://github.com/advisories/GHSA-w4gp-fjgq-3q4g (GitHub-reviewed advisory GHSA-w4gp-fjgq-3q4g lists affected ranges: npm happy-dom >=0 <20.8.9)

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