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.
Affected products
capricorn86: happy dom
References7
- github.com/capricorn86/happy-dom/security/advisories/GHSA-6q6h-… ExploitVendor Advisory
- github.com/capricorn86/happy-dom/security/advisories/GHSA-6q6h-… ExploitVendor Advisory
- github.com/capricorn86/happy-dom/commit/5437fdf8f13adb9590f9f52… Patch
- github.com/capricorn86/happy-dom/releases/tag/v20.8.8 ProductRelease Notes
- access.redhat.com/security/cve/CVE-2026-33943
- bugzilla.redhat.com/show_bug.cgi?id=2452522
- security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-33943…
Metrics
- CVSS 3.1
-
9.8
CRITICAL
Score source: NVD
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - EPSS — exploit probability
- 1% percentile: 51 · as of 12 November 2026
- CWE
- CWE-94CWE-917
Could this be exploited in your environment?
A patch closes the known hole. A penetration test shows what an attacker can still reach — with proof.