High · CVSS 8.8CVE-2026-115895GHSA-834V-8H66-3H79

Happy DOM: Incomplete fix for CVE-2026-33943: unsanitized import alias leads to host code executionCVE-2026-115895

Answer in brief

CVE-2026-115895 records a High severity (CVSS 8.8) vulnerability in Happy DOM: Incomplete fix for CVE-2026-33943: unsanitized import alias leads to host code execution. The current sources do not mark it as known exploited. The current feed maps capricorn86/happy-dom (generic), happy-dom (npm). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Oct 23, 2026Updated Oct 23, 2026Source checked Oct 23, 2026First seen by HOL Oct 23, 2026Material review Oct 23, 2026

Upstream Advisory

Key facts

Risk: High · CVSS 8.8
Exploitation: Not marked as known exploited
Affected software: 2 mapped packages or products
Fix availability: Available

Why this deserves its current priority

CVSS is 8.8. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps capricorn86/happy-dom (generic), happy-dom (npm). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
capricorn86/happy-domgeneric	>=17.0.0 <21.0.4	21.0.4
happy-domnpm	>=17.0.0,<=21.0.3	21.0.4

Recommended response

Check inventory. Check lockfiles and deployed manifests for capricorn86/happy-dom, happy-dom.
Review the reported fix. Update capricorn86/happy-dom to 21.0.4; happy-dom to 21.0.4 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Oct 23, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Oct 23, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Oct 23, 2026

Sources and claim methodology

Upstream source description

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.

Quoted source text, attributed separately from HOL analysis.