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CVE-2026-59952— Valibot: record() issue paths can make flatten() throw for inherited Object property names

Quick assessment

Affected
open-circle valibot
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Open Circle Valibot是Open Circle组织开源的一个用于结构化数据验证的库。 Open Circle valibot 1.4.2之前版本存在异常处理不当漏洞，该漏洞源于flatten() helper中对象键冲突导致TypeError，当验证问题包含攻击者控制的键时，可能导致请求路径崩溃，影响错误处理。

CVSS 6.9 · Medium EPSS 0.52% · P44

Possible ATT&CK Techniques 1 AI

T1135 · Network Share Discovery

Affected Version Matrix 1

VendorProduct Version RangeStatus
open-circle valibot < 1.4.2 affected
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I. Basic Information for CVE-2026-59952

Vulnerability Information
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Vulnerability Title
Valibot: record() issue paths can make flatten() throw for inherited Object property names
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
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
Source: CVE Program / CVE List V5
Vulnerability Type
对异常条件的处理不恰当
Source: CVE Program / CVE List V5
Vulnerability Title
Open Circle valibot 异常处理不当漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Open Circle Valibot是Open Circle组织开源的一个用于结构化数据验证的库。 Open Circle valibot 1.4.2之前版本存在异常处理不当漏洞，该漏洞源于flatten() helper中对象键冲突导致TypeError，当验证问题包含攻击者控制的键时，可能导致请求路径崩溃，影响错误处理。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
open-circle valibot < 1.4.2 -

II. Public POCs for CVE-2026-59952

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III. Intelligence Information for CVE-2026-59952

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Patches & Fixes for CVE-2026-59952 (2)

Vendor Advisories for CVE-2026-59952 (1)

Vendor Pages for CVE-2026-59952 (1)

IV. Related Vulnerabilities

Same product: valibot
Same vendor: open-circle
Same weakness: CWE-755

V. Comments for CVE-2026-59952

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