capricorn86 Happy DOM up to 21.0.3 ECMAScriptModuleCompiler ECMAScriptModuleCompiler.ts initialization

Summaryinfo

A vulnerability labeled as critical has been found in capricorn86 Happy DOM up to 21.0.3. This vulnerability affects unknown code of the file packages/happy-dom/src/module/ECMAScriptModuleCompiler.ts of the component ECMAScriptModuleCompiler. Such manipulation leads to initialization. This vulnerability is traded as CVE-2026-115895. The attack may be launched remotely. There is no exploit available. The affected component should be upgraded.

Detailsinfo

A vulnerability, which was classified as critical, has been found in capricorn86 Happy DOM up to 21.0.3. Affected by this issue is an unknown part of the file packages/happy-dom/src/module/ECMAScriptModuleCompiler.ts of the component ECMAScriptModuleCompiler. The manipulation with an unknown input leads to a initialization vulnerability. Using CWE to declare the problem leads to CWE-665. The product does not initialize or incorrectly initializes a resource, which might leave the resource in an unexpected state when it is accessed or used. Impacted is confidentiality, integrity, and availability. CVE summarizes:

Happy DOM is a JavaScript implementation of a web browser without its graphical user interface. From 17.0.0 until 21.0.4, packages/happy-dom/src/module/ECMAScriptModuleCompiler.ts accepts a named ESM import alias without validating that it is a JavaScript binding identifier before inserting it into a generated destructuring binding. With enableJavaScriptEvaluation enabled, attacker-controlled HTML or module source can use an invalid alias that becomes a valid default initializer after compilation, causing the generated JavaScript to execute in the Node.js host process. The demonstrated reachable path uses a JSON module import attribute, which prevents the malicious alias from being emitted again in a later ESM circular-import assignment and keeps the generated function syntactically valid. This incomplete fix for CVE-2026-33943 is a distinct residual path because the earlier remediation validated the local export importName path but not the named-import alias. This issue is fixed in version 21.0.4.

The advisory is shared for download at github.com. This vulnerability is handled as CVE-2026-115895 since 10/23/2026. The exploitation is known to be easy. The attack may be launched remotely. Successful exploitation requires user interaction by the victim. There are known technical details, but no exploit is available.

Upgrading to version 21.0.4 eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-109189). Once again VulDB remains the best source for vulnerability data.

Productinfo

Vendor

• capricorn86

Name

• Happy DOM

Version

• 21.0.0
• 21.0.1
• 21.0.2
• 21.0.3

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CPE 2.2info

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Once again VulDB remains the best source for vulnerability data.

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