CVE-2026-33943

CRITICALNVD 9.88.8▼
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 8.8 under NVD CVSS v3. EPSS exploit probability: 0.1%, top 75% of all CVEs by exploit prediction. 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: epss, nvd
Trending — 3 sources updated this weekElevated
9.8
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 1%CVSS: 9.8Exploit: NoneExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

Happy DOM is a JavaScript implementation of a web browser without its graphical user interface. In versions 15.10.0 through 20.8.7, a code injection vulnerability in ECMAScriptModuleCompiler allows an attacker to achieve Remote Code Execution (RCE) by injecting arbitrary JavaScript expressions inside export { } declarations in ES module scripts processed by happy-dom. The compiler directly interpolates unsanitized content into generated code as an executable expression, and the quote filter does not strip backticks, allowing template literal-based payloads to bypass sanitization. Version 20.8.8 fixes the issue.

CVSS v3
9.8
EG Score
8.8(medium)
EPSS
52.1%
KEV
Not listed

Published

March 27, 2026

Last Modified

July 15, 2026

Advisory Details (6)

Auto-updated Jul 16, 2026
🔬 Proof of concept available. Patch available. Sources: github_commit, github_release, github, redhat.
redhat
https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-33943.json
github Patch Available🟡 PoC Available

RCE in ECMAScriptModuleCompiler: unsanitized export names are interpolated as executable code · Advisory · capricorn86/happy-dom · GitHub

Affected: v15.10.2 and v20.0.0 respectively, but this vulnerable code path in

https://github.com/capricorn86/happy-dom/security/advisories/GHSA-6q6h-j7hj-3r64
redhat

2452522 – (CVE-2026-33943) CVE-2026-33943 happy-dom: Happy DOM: Remote Code Execution via JavaScript expression injection

https://bugzilla.redhat.com/show_bug.cgi?id=2452522
redhat Patch Available

cve-details

https://access.redhat.com/security/cve/CVE-2026-33943
github_release Patch Available

v20.8.8

Patch available: capricorn86/happy-dom v20.8.8

https://github.com/capricorn86/happy-dom/releases/tag/v20.8.8
github_commit Patch Available

commit 5437fdf8f13a (capricorn86/happy-dom)

Patch available: capricorn86/happy-dom v20.8.8 (contains commit 5437fdf8f13a)

https://github.com/capricorn86/happy-dom/commit/5437fdf8f13adb9590f9f52616d9f69c3ee8db3c

Affected Packages

(1 across 1 ecosystem)
npm(1)
PackageVulnerable rangeFixed inDependents
happy-dom—20.8.8—

Weakness Classification(2)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 11× in last 7d / 46× 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.

Showing the most recent 100 of 102 total refreshes for this CVE.

  1. 2026-07-16 17:03 UTCEPSS rescore
  2. 2026-07-15 16:57 UTCEPSS rescore
  3. 2026-07-15 16:57 UTCEPSS rescore
  4. 2026-07-15 02:22 UTCNVD updateCVSS v3 → 9.8 · severity → CRITICAL
  5. 2026-07-15 02:00 UTCEPSS rescore
  6. 2026-07-15 01:21 UTCMITRE cvelistV5CVSS v3 → 8.8 · severity → HIGH
  7. 2026-07-13 22:30 UTCEPSS rescore
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  22. 2026-06-30 23:22 UTCEPSS rescore
  23. 2026-06-30 04:32 UTCNVD updateCVSS v3 → 9.8 · severity → CRITICAL
  24. 2026-06-29 14:06 UTCEPSS rescore
  25. 2026-06-29 14:06 UTCEPSS rescore
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  1. 2026-06-29 03:32 UTCOSV refresh
  2. 2026-06-28 14:07 UTCEPSS rescore
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  23. 2026-06-15 17:49 UTCEPSS rescore
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  26. 2026-06-12 23:12 UTCEPSS rescore
  27. 2026-06-12 23:12 UTCEPSS rescore
  28. 2026-06-11 22:53 UTCEG score recompute
  29. 2026-06-11 14:00 UTCEPSS rescore
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  39. 2026-06-07 15:25 UTCEPSS rescore
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  42. 2026-06-07 11:51 UTCEG score recompute
  43. 2026-06-06 13:47 UTCEPSS rescore
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  45. 2026-06-05 22:47 UTCEPSS rescore
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  55. 2026-06-01 05:43 UTCOSV refresh
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  72. 2026-05-23 00:09 UTCEG score recompute
  73. 2026-05-20 22:38 UTCEPSS rescore
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  75. 2026-05-20 20:01 UTCEG score recompute

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-33943?
CVE-2026-33943 is a critical vulnerability published on March 27, 2026. Happy DOM is a JavaScript implementation of a web browser without its graphical user interface. In versions 15.10.0 through 20.8.7, a code injection vulnerability in ECMAScriptModuleCompiler allows an attacker to achieve Remote Code Execution (RCE) by injecting arbitrary JavaScript expressions…
When was CVE-2026-33943 disclosed?
CVE-2026-33943 was first published in the National Vulnerability Database on March 27, 2026, with the most recent update on July 15, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-33943 actively exploited?
CVE-2026-33943 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 52.1% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-33943?
CVE-2026-33943 has a CVSS v3 base score of 9.8 (NVD). EchelonGraph synthesises NVD + CISA KEV + FIRST EPSS + GHSA into a combined EG score of 8.8.
How do I remediate CVE-2026-33943?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-33943, 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

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