CVE-2026-115895
Happy DOM: Incomplete fix for CVE-2026-33943: unsanitized import alias leads to host code execution
High 8.8
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.
GitHub_M
2026-10-23
2026-10-23
2026-10-23
Seen in other sources
- GitHub advisory GHSA-834v-8h66-3h79
2026-10-23 ·
same day as publication
Happy DOM: Incomplete fix for CVE-2026-33943: unsanitized import alias leads to host code execution
Scores
| Source | CVSS | Score | Severity | Vector |
|---|---|---|---|---|
| GitHub_M | 3.1 | 8.8 | High | CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H |
Weaknesses
Affected
| Vendor | Product | Versions |
|---|---|---|
| capricorn86 | happy-dom | >= 17.0.0, < 21.0.4 (affected) |
References
- https://github.com/capricorn86/happy-dom/security/advisories/GHSA-834v-8h66-3h79 x_refsource_CONFIRM
- https://github.com/capricorn86/happy-dom/pull/2537 x_refsource_MISC
- https://github.com/capricorn86/happy-dom/commit/fd163520b74d9fa146be91f7b4e4f46d6cccbe13 x_refsource_MISC
- https://github.com/capricorn86/happy-dom/releases/tag/v21.0.4 x_refsource_MISC
Full CVE JSON record (5.2)
{
"containers": {
"cna": {
"affected": [
{
"product": "happy-dom",
"vendor": "capricorn86",
"versions": [
{
"status": "affected",
"version": "\u003e= 17.0.0, \u003c 21.0.4"
}
]
}
],
"descriptions": [
{
"lang": "en",
"value": "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."
}
],
"metrics": [
{
"cvssV3_1": {
"attackComplexity": "LOW",
"attackVector": "NETWORK",
"availabilityImpact": "HIGH",
"baseScore": 8.8,
"baseSeverity": "HIGH",
"confidentialityImpact": "HIGH",
"integrityImpact": "HIGH",
"privilegesRequired": "NONE",
"scope": "UNCHANGED",
"userInteraction": "REQUIRED",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H",
"version": "3.1"
}
}
],
"problemTypes": [
{
"descriptions": [
{
"cweId": "CWE-94",
"description": "CWE-94: Improper Control of Generation of Code (\u0027Code Injection\u0027)",
"lang": "en",
"type": "CWE"
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-10-23T21:32:24.999Z",
"orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
"shortName": "GitHub_M"
},
"references": [
{
"name": "https://github.com/capricorn86/happy-dom/security/advisories/GHSA-834v-8h66-3h79",
"tags": [
"x_refsource_CONFIRM"
],
"url": "https://github.com/capricorn86/happy-dom/security/advisories/GHSA-834v-8h66-3h79"
},
{
"name": "https://github.com/capricorn86/happy-dom/pull/2537",
"tags": [
"x_refsource_MISC"
],
"url": "https://github.com/capricorn86/happy-dom/pull/2537"
},
{
"name": "https://github.com/capricorn86/happy-dom/commit/fd163520b74d9fa146be91f7b4e4f46d6cccbe13",
"tags": [
"x_refsource_MISC"
],
"url": "https://github.com/capricorn86/happy-dom/commit/fd163520b74d9fa146be91f7b4e4f46d6cccbe13"
},
{
"name": "https://github.com/capricorn86/happy-dom/releases/tag/v21.0.4",
"tags": [
"x_refsource_MISC"
],
"url": "https://github.com/capricorn86/happy-dom/releases/tag/v21.0.4"
}
],
"source": {
"advisory": "GHSA-834v-8h66-3h79",
"discovery": "UNKNOWN"
},
"title": "Happy DOM: Incomplete fix for CVE-2026-33943: unsanitized import alias leads to host code execution"
}
},
"cveMetadata": {
"assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
"assignerShortName": "GitHub_M",
"cveId": "CVE-2026-115895",
"datePublished": "2026-10-23T21:32:24.999Z",
"dateReserved": "2026-10-23T19:37:27.177Z",
"dateUpdated": "2026-10-23T21:32:24.999Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}