Description
Valibot helps validate data using a schema. Versions prior to 1.4.2 can throw a TypeError inside its flatten() helper when validation issues contain attacker-controlled object keys such as toString, valueOf, or hasOwnProperty. The issue is reachable through normal record() validation. record() intentionally filters __proto__, prototype, and constructor, but it still accepts other own keys that collide with inherited Object.prototype properties. If the record key schema or value schema rejects such an entry, Valibot creates an issue path containing that key. Passing the resulting issues to Valibot's documented flatten() helper causes flatErrors.nested[dotPath] to resolve to the inherited method instead of an own error array, and the helper calls .push(...) on that function. This is not a global prototype pollution issue. The impact is availability/error handling: applications that validate user-controlled objects with record() and flatten validation errors for API responses can crash the request path with a TypeError instead of returning structured validation errors. This issue has been fixed in version 1.4.2.
Published: 2026-07-30
Score: 6.9 Medium
EPSS: n/a
KEV: No
Impact: n/a
Action: n/a
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Remediation

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Tracking

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Advisories
Source ID Title
Github GHSA Github GHSA GHSA-5qjj-4xww-7phc Valibot: record() issue paths can make flatten() throw for inherited Object property names
History

Thu, 30 Jul 2026 01:00:00 +0000

Type Values Removed Values Added
Description Valibot helps validate data using a schema. Versions prior to 1.4.2 can throw a TypeError inside its flatten() helper when validation issues contain attacker-controlled object keys such as toString, valueOf, or hasOwnProperty. The issue is reachable through normal record() validation. record() intentionally filters __proto__, prototype, and constructor, but it still accepts other own keys that collide with inherited Object.prototype properties. If the record key schema or value schema rejects such an entry, Valibot creates an issue path containing that key. Passing the resulting issues to Valibot's documented flatten() helper causes flatErrors.nested[dotPath] to resolve to the inherited method instead of an own error array, and the helper calls .push(...) on that function. This is not a global prototype pollution issue. The impact is availability/error handling: applications that validate user-controlled objects with record() and flatten validation errors for API responses can crash the request path with a TypeError instead of returning structured validation errors. This issue has been fixed in version 1.4.2.
Title Valibot: record() issue paths can make flatten() throw for inherited Object property names
Weaknesses CWE-755
References
Metrics cvssV4_0

{'score': 6.9, 'vector': 'CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N'}

Subscriptions

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cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-07-30T00:10:32.598Z

Reserved: 2026-07-07T18:49:15.607Z

Link: CVE-2026-59952

cve-icon Vulnrichment

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cve-icon NVD

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cve-icon Redhat

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cve-icon OpenCVE Enrichment

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Weaknesses