CVE-2026-33943
HIGHDescription
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.
How to fix
TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works
Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.
CVSS v3 Vector
Exploitability
Impact
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Exploit Intelligence
Moderate risk: more likely to be exploited than 53% of all known CVEs.
References
Related Vulnerabilities
Other CWE-94 (Code Injection) vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2017-9841 | Critical | 9.8 | 100% | KEV | Fix |
| CVE-2015-1635 | Critical | 9.8 | 100% | KEV | - |
| CVE-2022-22954 | Critical | 9.8 | 100% | KEV + Ransom | - |
| CVE-2025-3248 | Critical | 9.8 | 100% | KEV + Ransom | Fix |
| CVE-2025-49704 | High | 8.8 | 100% | KEV + Ransom | Fix |
| CVE-2021-22204 | Medium | 6.8 | 100% | KEV | Fix |
Common questions
How do I fix CVE-2026-33943?
Upgrade happy dom to 20.8.8 or later.
Is CVE-2026-33943 being actively exploited?
Not that we know of. CVE-2026-33943 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 0.79% is the estimated probability that it will be exploited in the next 30 days. That is higher than 53% of all scored CVEs.
How severe is CVE-2026-33943?
CVE-2026-33943 has a CVSS v3 base score of 8.8, rated high. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
What does CVE-2026-33943 affect?
Published advisories record a fix for happy dom (NVD). Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.
Embed a live status badge for CVE-2026-33943
Markdown
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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-07-15.