CVE-2026-33943
What it is
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.
At a glance
- Exploitability
- Can be exploited over the network without logging in, but needs a user to act. High risk of data exposure, data tampering, service disruption.
- Exploit odds
- 0.6% chance of exploitation in the next 30 days (EPSS).
- Fix
- A patch, advisory or fixed version is referenced. Upgrade or apply it.
Timeline
- PublishedDisclosed publicly on CVE.org and NVD
- Last updatedMost recent change to the record
Why it ranks here
- Exploited in the wild: no, CISA does not list it.
- Exploit odds: 0.6% in the next 30 days (EPSS).
- Severity: 8.8 HIGH (CVSS).
- Fix: a patch or advisory is linked.
Details
- Published
- Last modified
- Exploit probability
- 0.6% · EPSS, next 30 days
- Weakness
- CWE-94 · Code injection
- Record status
- Modified
Affected
- capricorn86 Happy Dom < 20.8.8
Attack profile CVSS 3.1 · 8.8
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- Required
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
Raw vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Is it in your code?
Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.
Read https://cve-list.com/agent/cve/CVE-2026-33943.md and follow it. Check whether this project is affected by CVE-2026-33943. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.
Fix and advisories
- https://github.com/capricorn86/happy-dom/commit/5437fdf8f13adb9590f9f52616d9f69c3ee8db3c
- https://github.com/capricorn86/happy-dom/releases/tag/v20.8.8
- https://github.com/capricorn86/happy-dom/security/advisories/GHSA-6q6h-j7hj-3r64
- https://github.com/capricorn86/happy-dom/security/advisories/GHSA-6q6h-j7hj-3r64
References
- https://github.com/capricorn86/happy-dom/commit/5437fdf8f13adb9590f9f52616d9f69c3ee8db3c
- https://github.com/capricorn86/happy-dom/releases/tag/v20.8.8
- https://github.com/capricorn86/happy-dom/security/advisories/GHSA-6q6h-j7hj-3r64
- 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-3r64
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-33943.json