Request interruption via inherited-key error collision
Published Jul 30, 2026 · Updated Jul 30, 2026
Improper exception handling in Open Circle Valibot before 1.4.2 allows remote attackers to interrupt request handling via crafted object keys. The flatten() helper stores nested errors in a plain object, treats an inherited Object.prototype method as an existing array, and calls push() on it. Reachability requires an application to validate attacker-controlled records and flatten a rejected inherited-name key; the request path then throws a TypeError instead of returning structured errors.
Summary
What happened
Improper exception handling in Open Circle Valibot before 1.4.2 allows remote attackers to interrupt request handling via crafted object keys. The flatten() helper stores nested errors in a plain object, treats an inherited Object.prototype method as an existing array, and calls push() on it. Reachability requires an application to validate attacker-controlled records and flatten a rejected inherited-name key; the request path then throws a TypeError instead of returning structured errors.
The record
- CVE
- CVE-2026-59952
- Published
- Jul 30, 2026
- Updated
- Jul 30, 2026
- Vendor
- Open Circle
- Product
- Valibot
- Classifications
- CWE-755, T1499.004
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Jul 30, 2026CVE publishedPublication date reported by the CVE source.
- Jul 30, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=< 1.4.2
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
- GitHub advisory local reproductionproof of concept · demonstrated
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Technologies
Your stack
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Your stack
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