Svelte devalue is a JavaScript library that serializes values into strings when JSON.stringify isn't sufficient for the job. From 5.3.0 to 5.6.1, certain inputs can cause devalue.parse to consume excessive CPU time and/or memory, potentially leading to denial of service in systems that parse input from untrusted sources. This affects applications using devalue.parse on externally-supplied data.

The root cause is the typed array hydration expecting an ArrayBuffer as input, but not checking the assumption before creating the typed array. This vulnerability is fixed in 5.6.2.