SEPTEMBER 19, 2026
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Case File

CVE-2026-59952

MEDIUM · CVSS 6.9 EPSS 0.30% Public Exploit

Source: NVD + CISA KEV + EPSS · Published 2026-07-30 · Last synced 2026-08-29

CyberRota Analysis

AI-Generated

Valibot versions prior to 1.4.2 are vulnerable to a TypeError in the flatten() helper when processing validation issues that include attacker-controlled object keys, potentially leading to application crashes instead of structured error responses. This vulnerability affects applications that utilize Valibot for validating user-controlled objects through the record() function, making it critical for developers and security teams using this library to prioritize upgrading to version 1.4.2 to mitigate the risk of availability issues.

Public Exploit Signal

A public exploit, PoC, GitHub repository or Metasploit reference was detected for this CVE.

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CVE
CVE-2026-59952
Severity
MEDIUM
CVSS
6.9
EPSS
0.30%

Original NVD 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.