CVE-2026-33943

Name: CVE-2026-33943
Creator: NVD / NIST
Published: 2026-03-27T22:16:21.393+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

CRITICALCVSS 9.8/10EPSS 0.74%

Last modified Jun 17, 2026

CVE-2026-33943 is a critical-severity vulnerability rated 9.8/10 on the CVSS scale. 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. EPSS estimates a 0.74% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 3.1

9.8/10

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

EPSS Probability

0.74%

50.0th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-94

Affected Software

Vendor	Product	Versions
Capricorn86	Happy Dom	>= 15.10.0, < 20.8.8

References

https://github.com/capricorn86/happy-dom/commit/5437fdf8f13adb9590f9f52616d9f69c3ee8db3cPatch
https://github.com/capricorn86/happy-dom/releases/tag/v20.8.8Product, Release Notes
https://github.com/capricorn86/happy-dom/security/advisories/GHSA-6q6h-j7hj-3r64Exploit, Vendor Advisory
https://github.com/capricorn86/happy-dom/security/advisories/GHSA-6q6h-j7hj-3r64Exploit, Vendor Advisory

Timeline

Published: Mar 27, 2026
Last Modified: Jun 17, 2026
Status: Analyzed

Frequently Asked Questions

What is CVE-2026-33943?

How severe is CVE-2026-33943?

CVE-2026-33943 has a CVSS score of 9.8/10 (CRITICAL severity). The EPSS model estimates a 0.74% probability of exploitation in the next 30 days.

How do I fix CVE-2026-33943?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2026-33943?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST