CVE-2026-33943

critical

Happy DOM is a JavaScript implementation of a web browser without its graphical user interface.

Vendor / product: Capricorn86 — happy dom

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

9.8

9.8 (CVSS v3.1)

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

Severity source: NVD CVSS v3.1 (nvd@nist.gov)

Timeline (UTC)

Published: 2026-03-27 22:16

Modified: 2026-10-26 00:10

NVD status: Modified

Last synced 2 days ago

Verified against the source API 2026-10-27 07:07 UTC

Exploitation

Not listed in CISA KEV (as of last catalog sync)

Absence from KEV does not mean a CVE is not exploited. Exploitation status: unknown (no authoritative evidence in our sources).

Affected products

capricorn86 / happy_dom ≥15.10.0 <20.8.8

Weakness classification (CWE)

CWE-94 CWE-917

Source: NVD / CISA. “NVD-CWE-Other” and “NVD-CWE-noinfo” mean NVD could not assign a specific weakness.

Mitigation & advisories

Vendor advisory: https://github.com/capricorn86/happy-dom/security/advisories/GHSA-6q6h-j7hj-3r64

Patch / mitigation: https://github.com/capricorn86/happy-dom/commit/5437fdf8f13adb9590f9f52616d9f69c3ee8db3c

References

https://github.com/capricorn86/happy-dom/commit/5437fdf8f13adb9590f9f52616d9f69c3ee8db3c security-advisories@github.com
https://github.com/capricorn86/happy-dom/releases/tag/v20.8.8 security-advisories@github.com
https://github.com/capricorn86/happy-dom/security/advisories/GHSA-6q6h-j7hj-3r64 security-advisories@github.com
https://access.redhat.com/security/cve/CVE-2026-33943 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
https://bugzilla.redhat.com/show_bug.cgi?id=2452522 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
https://github.com/capricorn86/happy-dom/security/advisories/GHSA-6q6h-j7hj-3r64 134c704f-9b21-4f2e-91b3-4a467353bcc0
https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-33943.json 0b0ca135-0b70-47e7-9f44-1890c2a1c46c

Data sources

NVD CVE API 2.0 — fetched 2026-10-27 07:07 UTC · record ↗

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