CVE-2026-33943
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…
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (0.79%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
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.
- CVSS 3.1
- 9.8 CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- EPSS
- 0.79% probability · 54th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-94, CWE-917
- Affected
- capricorn86/happy dom
- Source
- security-advisories@github.com
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://access.redhat.com/security/cve/CVE-2026-33943
- https://bugzilla.redhat.com/show_bug.cgi?id=2452522
- https://github.com/capricorn86/happy-dom/security/advisories/GHSA-6q6h-j7hj-3r64Exploit, Vendor Advisory
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-33943.json
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.