CVE-2026-59952
Valibot: record() issue paths can make flatten() throw for inherited Object property names
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.
INFO
Published Date :
July 30, 2026, 1:17 a.m.
Last Modified :
Oct. 23, 2026, 10:10 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | |||||
| CVSS 4.0 | MEDIUM | [email protected] |
Solution
- Update Valibot to version 1.4.2 or later.
- Avoid using untrusted object keys in record validation.
- Implement custom validation for object keys if upgrading is not possible.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-59952.
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-59952 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-59952
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
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The following list is the news that have been mention
CVE-2026-59952 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-59952 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
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CVE Translated by [email protected]
Oct. 23, 2026
Action Type Old Value New Value Added Translation Title: valibot de open-circle, Description: Valibot ayuda a validar datos usando un esquema. Las versiones anteriores a la 1.4.2 pueden lanzar un TypeError dentro de su ayudante flatten() cuando los problemas de validación contienen claves de objeto controladas por el atacante, como toString, valueOf o hasOwnProperty. El problema es alcanzable a través de la validación normal de record(). record() filtra intencionadamente __proto__, prototype y constructor, pero aún acepta otras claves propias que colisionan con propiedades heredadas de Object.prototype. Si el esquema de clave de registro o el esquema de valor rechaza dicha entrada, Valibot crea una ruta de problema que contiene esa clave. Pasar los problemas resultantes al ayudante flatten() documentado de Valibot hace que flatErrors.nested[dotPath] se resuelva al método heredado en lugar de una matriz de errores propia, y el ayudante llama a .push(...) en esa función. Esto no es un problema de contaminación global de prototipos. El impacto es disponibilidad/manejo de errores: las aplicaciones que validan objetos controlados por el usuario con record() y aplanan los errores de validación para las respuestas de la API pueden bloquear la ruta de la solicitud con un TypeError en lugar de devolver errores de validación estructurados. Este problema ha sido corregido en la versión 1.4.2. -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Jul. 30, 2026
Action Type Old Value New Value Added Reference https://github.com/open-circle/valibot/security/advisories/GHSA-5qjj-4xww-7phc Added SSVC {'id': 'CVE-2026-59952', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'poc'}, {'automatable': 'yes'}, {'technicalImpact': 'partial'}], 'version': '2.0.3', 'timestamp': '2026-07-30T14:41:28.900290Z'} -
New CVE Received by [email protected]
Jul. 30, 2026
Action Type Old Value New Value Added Affected [{'vendor': 'open-circle', 'product': 'valibot', 'versions': [{'status': 'affected', 'version': '< 1.4.2'}]}] 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. Added CVSS V4.0 AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X Added CWE CWE-755 Added Reference https://github.com/open-circle/valibot/commit/1bd01c304657cd0809cc92694360b6cc60f700bf Added Reference https://github.com/open-circle/valibot/pull/1522 Added Reference https://github.com/open-circle/valibot/releases/tag/v1.4.2 Added Reference https://github.com/open-circle/valibot/security/advisories/GHSA-5qjj-4xww-7phc