CVE-2026-42570 HIGH

CVE-2026-42570: Svelte devalue: DoS via sparse array deserialization

Vendor Sveltejs
Product devalue
Weakness CWE-770 · Uncontrolled resource consumption
Published June 9, 2026
Last update June 30, 2026

CVSS base score

7.5/10
Attack vector Network
Attack complexity Low
Privileges required None
User interaction None
Confidentiality None
Integrity None

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

What the vulnerability does

01Description

Svelte devalue is a JavaScript library that serializes values into strings when JSON.stringify isn't sufficient for the job. From version 5.6.3 to before version 5.8.1, devalue.parse could, due to quirks in some JavaScript engines, be convinced to allocate much more memory than was needed when deserializing sparse arrays, leading to excessive memory consumption. This issue has been patched in version 5.8.1.

Key dates

02Disclosure timeline

June 9, 2026 CVE published
June 30, 2026 Record updated