Vulnerability in valibot (CVE-2026-59952)
Summary
Vulnerability in valibot (CVE-2026-59952). Risk of unauthorized operations or information disclosure. Exploitable via valibot. Mitigation: upgrade to 1.2.0 or later.
Original description
The description as published by the source.
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: GitHub Security Advisories (Global) NVD GitHub Advisory
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-59952 has been found in valibot.
Attackers can target a specific entry point like valibot over the network to misuse the product.
Risk of unauthorized operations or information disclosure.
What to do: upgrade valibot to 1.2.0 or later.
If unsure, ask your IT team or search "valibot CVE-2026-59952" on the vendor's site.
CVE-2026-59952 (valibot) — CWE-755
Attack surface: valibot / TypeError / toString / valueOf
Patched: 1.2.0 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
A vulnerability (CWE-755) exists in valibot. Attackers reach the vulnerable code path via valibot.
Check the vendor advisory for the affected versions of valibot. Attack surface: valibot / TypeError / toString / valueOf.
Severity: ?. Risk of unauthorized operations or information disclosure.
Update to 1.2.0.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'valibot' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
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1Identify exposure identify
grep -r 'valibot' . | grep -v node_modulesリポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で
valibotを grep し、稼働しているサービス・バージョンを把握する。 -
2Apply patch patch
Upgrade valibot to 1.2.0ステージング環境で 1.2.0 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。
-
3Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
Affected packages
References
- advisory github.com
- advisory github.com
- advisory nvd.nist.gov
- package github.com
- patch github.com
- patch github.com
- web github.com
- web github.com