CVE-2026-33943

Happy DOM ECMAScriptModuleCompiler: unsanitized export names are interpolated as executable code

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.

Affected

capricorn86 · happy-dom

CVSS v3.1 NVD

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

CVSS v3.1 CNA

8.8 HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

EPSS

0.97% chance of exploitation in the next 30 days, 61st percentile

Published

2026-03-27

Updated

2026-07-15

Proof-of-concept exploits (1)

• advisories/GHSA-6q6h-j7hj-3r64

Security advisories

• capricorn86/happy-dom/security/advisories/GHSA-6q6h-j7hj-3r64
• capricorn86/happy-dom/commit/5437fdf8f13adb9590f9f52616d9f69c3ee8db3c

References

• CVE Record
• NVD entry