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

Summary

CVE	CVE-2026-33943
State	PUBLISHED
Assigner	GitHub_M
Source Priority	CVE Program / NVD first with legacy fallback
Published	2026-03-27 22:16:21 UTC
Updated	2026-07-15 02:20:26 UTC
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.

Risk And Classification

Primary CVSS: v3.1 9.8 CRITICAL from [email protected]

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

EPSS: 0.007880000 probability, percentile 0.520540000 (date 2026-07-16)

Problem Types: CWE-94 | CWE-917 | CWE-94 CWE-94: Improper Control of Generation of Code ('Code Injection') | CWE-917 Improper Neutralization of Special Elements used in an Expression Language Statement ('Expression Language Injection')

Version	Source	Type	Score	Severity	Vector
3.1	[email protected]	Primary	9.8	CRITICAL	`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`
3.1	ADP	CVSS	8.8	HIGH	`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H`
3.1	[email protected]	Secondary	8.8	HIGH	`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H`
3.1	0b0ca135-0b70-47e7-9f44-1890c2a1c46c	Secondary	8.8	HIGH	`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H`
3.1	CNA	DECLARED	8.8	HIGH	`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H`

CVSS v3.1 Breakdown

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

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

NVD Known Affected Configurations (CPE 2.3)

Type	Vendor	Product	Version	Update	Edition	Language
Application	Capricorn86	Happy Dom	All	All	All	All

Vendor Declared Affected Products

Source	Vendor	Product	Version	Platforms
CNA	Capricorn86	Happy-dom	affected >= 15.10.0, < 20.8.8	Not specified
ADP	Red Hat	Red Hat Ansible Automation Platform 2	Not specified	Not specified
ADP	Red Hat	Red Hat OpenShift Container Platform 4	Not specified	Not specified

References

Reference	Source	Link	Tags
bugzilla.redhat.com/show_bug.cgi	0b0ca135-0b70-47e7-9f44-1890c2a1c46c	bugzilla.redhat.com
github.com/capricorn86/happy-dom/security/advisories/GHSA-6q6h-j7hj-3r64	134c704f-9b21-4f2e-91b3-4a467353bcc0	github.com	Exploit, Vendor Advisory
github.com/capricorn86/happy-dom/commit/5437fdf8f13adb9590f9f52616d9f69c...	[email protected]	github.com	Patch
github.com/capricorn86/happy-dom/releases/tag/v20.8.8	[email protected]	github.com	Product, Release Notes
access.redhat.com/security/cve/CVE-2026-33943	0b0ca135-0b70-47e7-9f44-1890c2a1c46c	access.redhat.com
security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-33943.json	0b0ca135-0b70-47e7-9f44-1890c2a1c46c	security.access.redhat.com
CVE Program record	CVE.ORG	www.cve.org	canonical
NVD vulnerability detail	NVD	nvd.nist.gov	canonical, analysis

No vendor comments have been submitted for this CVE.

Additional Advisory Data

Source	Time	Event
ADP	2026-03-27T22:02:46.904Z	Reported to Red Hat.
ADP	2026-03-27T21:15:19.186Z	Made public.

Workarounds

ADP: Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.

There are currently no legacy QID mappings associated with this CVE.