CVE-2026-33943CRITICAL 8.8EPSS p52.6%

CVE-2026-33943CVE-2026-33943

capricorn86 / happy_dom

Description

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.

Scoring

CVSS 3.18.8 (CRITICAL)
VectorCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
EPSS0.79% probability of exploitation · percentile 52.6% · 2026-08-03T12:00:16Z
Published2026-03-27
Last modified2026-07-15

Underlying weaknesses· 1

CWE-94

References

  1. https://github.com/capricorn86/happy-dom/commit/5437fdf8f13adb9590f9f52616d9f69c3ee8db3c
  2. https://github.com/capricorn86/happy-dom/releases/tag/v20.8.8
  3. https://github.com/capricorn86/happy-dom/security/advisories/GHSA-6q6h-j7hj-3r64
  4. https://github.com/capricorn86/happy-dom/security/advisories/GHSA-6q6h-j7hj-3r64

1

TypeTargetConfidenceTier
WeaknessImproper Control of Generation of Code ('Code Injection')cwe-940%live

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Sourced from NVD + FIRST.org EPSS. Curated for EU compliance use cases by Adam Lundqvist, Founder at SQUR.