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.
CVE-2026-34226
HIGHPre-NVD 7.57.5
EchelonGraph scoreLOW confidence
This high-severity CVE scores 7.5 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit-prediction score not yet available (the EPSS model rescores nightly; freshly-published CVEs typically appear within 48 hours). GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).
Triggered by: NVD CVSS baseline
Sources: secondary
7.5
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
- High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 0%CVSS: 7.5Exploit: NoneExposed: 0
No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.
- CVSS v3
- 7.5
- EG Score
- 7.5(low)
- EPSS
- 36.7%
- KEV
- Not listed
Published
March 27, 2026
Last Modified
June 30, 2026
Advisory Details (8)
Auto-updated Jul 6, 2026🔬 Proof of concept available. Patch available. Sources: github_commit, github_pr, github_release, github, redhat.
redhat
2452519 – (CVE-2026-34226) CVE-2026-34226 happy-dom: Happy DOM: Information disclosure via incorrect cookie handling in fetch requests
https://bugzilla.redhat.com/show_bug.cgi?id=2452519github Patch Available🟡 PoC Available
fetch credentials include uses page-origin cookies instead of target-origin cookies · Advisory · capricorn86/happy-dom · GitHub
https://github.com/capricorn86/happy-dom/security/advisories/GHSA-w4gp-fjgq-3q4ggithub_release Patch Available
v20.8.9
Patch available: capricorn86/happy-dom v20.8.9
https://github.com/capricorn86/happy-dom/releases/tag/v20.8.9github_pr Patch Available
fix: [#0] Fixes issue where cookies from the current origin was being forwarded to the target origin in fetch requests
Patch available: capricorn86/happy-dom v20.8.9 (PR #2117 merged 2026-03-26)
https://github.com/capricorn86/happy-dom/pull/2117github_commit Patch Available
commit 68324c21d7b9 (capricorn86/happy-dom)
Patch available: capricorn86/happy-dom v20.8.9 (contains commit 68324c21d7b9)
https://github.com/capricorn86/happy-dom/commit/68324c21d7b98f53f7bb5a7b3e185bda7106e751generic
happy-dom/packages/happy-dom/src/fetch/utilities/FetchRequestHeaderUtility.ts at f8d8cad41e9722fab9eefb9dfb3cca696462e908 · capricorn86/happy-dom · GitHub
https://github.com/capricorn86/happy-dom/blob/f8d8cad41e9722fab9eefb9dfb3cca696462e908/packages/happy-dom/src/fetch/utilities/FetchRequestHeaderUtility.tsAffected Packages
(1 across 1 ecosystem)
npm(1)
| Package | Vulnerable range | Fixed in | Dependents |
|---|---|---|---|
| happy-dom | — | 20.8.9 | — |
Weakness Classification(2)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Data Freshness Timeline
(refreshed 9× in last 7d / 14× in last 30d)
Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.
- 2026-07-11 08:27 UTCEPSS rescore
- 2026-07-09 19:10 UTCEPSS rescore
- 2026-07-08 15:15 UTCEPSS rescore
- 2026-07-07 13:46 UTCEPSS rescore
- 2026-07-06 16:27 UTCEPSS rescore
- 2026-07-06 16:27 UTCEPSS rescore
- 2026-07-06 02:23 UTCEPSS rescore
- 2026-07-06 02:23 UTCEPSS rescore
- 2026-07-05 02:30 UTCEPSS rescore
- 2026-07-04 06:31 UTCEPSS rescore
- 2026-07-01 15:06 UTCEPSS rescore
- 2026-06-30 23:22 UTCEPSS rescore
- 2026-06-30 04:36 UTCEG score recompute
- 2026-06-30 04:32 UTCNVD updatefirst tracked
Frequently asked(5)
What is CVE-2026-34226?
CVE-2026-34226 is a high vulnerability published on March 27, 2026. 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…
When was CVE-2026-34226 disclosed?
CVE-2026-34226 was first published in the National Vulnerability Database on March 27, 2026, with the most recent update on June 30, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-34226 actively exploited?
CVE-2026-34226 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 36.7% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-34226?
CVE-2026-34226 has a CVSS v3 base score of 7.5 (NVD). The EG score is currently aggregating — additional source signals are being incorporated as they become available..
How do I remediate CVE-2026-34226?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-34226, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.
Dependency Blast Radius
See which npm, PyPI, Go, and Maven packages are affected by CVE-2026-34226
Is Your Infrastructure Affected by CVE-2026-34226?
EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.