Secuno
ENNL
Book demo

CVE-2026-33943

Capricorn86 Happy Dom remote code execution

8.8 HIGHPublic exploitEPSS 0.97%
  1. Published27 Mar 2026

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 breakdown

Attack vectorNetwork
Attack complexityLow
Privileges requiredNone
User interactionRequired
ScopeUnchanged
ConfidentialityHigh
IntegrityHigh
AvailabilityHigh
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

Affected products

Capricorn86 Happy Dom≥ 15.10.0 < 20.8.8

Remediation

Fixed in
Capricorn86 Happy Dom≥ 20.8.8

References

Related CVEs

Recent high-severity vulnerabilities sharing a weakness type.

CVE-2026-891079.9
SAP S/4HANA (Manage Substitution/Validation Rules) does not sufficiently validate input…
CVE-2026-961199.9
IBM i 7.3, 7.4, 7.5, and 7.6 could allow a remote authenticated attacker to obtain…
CVE-2026-821088.8
IBM DataStage on Cloud Pak for Data 5.4.0.0 could allow a remote authenticated attacker…
CVE-2026-909209.8
IBM Maximo AI Service 9.1.0, and 9.2.0 could allow a remote attacker to execute…
CVE-2026-185378.7
IBM Maximo Application Suite - Location Service for Esri Component 9.2, 9.1, and 9.0 is…
CVE-2026-1093088.8
Craft CMS 4.0.0 before 4.18.7 and 5.0.0 before 5.10.14 passes the raw 'updates' request…

Frequently asked

Is CVE-2026-33943 being actively exploited?

CVE-2026-33943 is not in the CISA KEV catalog. A public exploit reference exists, so treat it as exploitable. Its EPSS exploit probability is 0.97%.

How severe is CVE-2026-33943?

CVE-2026-33943 has a CVSS 3.1 base score of 8.8, rated high. EPSS estimates a 0.97% probability of exploitation.

Which products are affected by CVE-2026-33943?

Affected products include Capricorn86 Happy Dom.

How do I fix CVE-2026-33943?

Upgrade affected software to a fixed version, for example Capricorn86 Happy Dom 20.8.8 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2026-33943 against the real software inventory on every managed device, as each hourly inventory arrives. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

See how prioritisation worksBook a demo

Get Patch this first every Monday

Five vulnerabilities that matter this week, ranked on real exploitation. Plain language, one email, no spam.

You can unsubscribe with one click from every issue. We handle your details as described in our privacy policy.

Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.