CVE-2026-42570: Svelte Devalue

High severity, CVSS 7.5. EPSS: 0.7% chance of exploitation in the next 30 days.

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.

Affected products

• Svelte Devalue: from 5.6.3, before 5.8.1 (fixed in 5.8.1)

Published 2026-06-09. Last modified 2026-08-24.