A flaw was found in the Svelte devalue JavaScript library. A remote attacker could exploit a prototype pollution vulnerability by sending maliciously crafted payloads to the devalue.parse or devalue.unflatten functions. Successful exploitation of this flaw could lead to a Denial of Service (DoS) condition, making the affected system unavailable, or result in type confusion, which could have further unpredictable impacts.

Svelte devalue is a JavaScript library that serializes values into strings when JSON.stringify isn't sufficient for the job. In devalue v5.6.3 and earlier, devalue.parse and devalue.unflatten were susceptible to prototype pollution via maliciously crafted payloads. Successful exploitation could lead to Denial of Service (DoS) or type confusion. This vulnerability is fixed in 5.6.4.

devalue has prototype pollution in devalue.parse and devalue.unflatten