Svelte devalue is a JavaScript library that serializes values into strings when JSON.stringify isn't sufficient for the job. In versions 5.1.0 through 5.9.2, stringify and uneval functions serialize a typed array by emitting its entire backing ArrayBuffer rather than only the view, so serializing a Node Buffer, whose backing store is a process-wide shared pool, discloses up to 64 KB of unrelated process memory, including bytes from other in-flight requests. In a server-side-rendered framework such as SvelteKit or Nuxt, a public page whose load() returns a small Buffer, or that reads a small file, can therefore ship another user's request body or Authorization header in its HTML without authentication. Because this occurs during serialization, it fires on every such render and is not mitigated by the parse/unflatten prototype-pollution and denial-of-service guards, which only apply when parsing untrusted input. As a workaround, convert Node Buffer objects to Uint8Array before serialization. This issue has been fixed in version 5.9.3.

Impact

devalue.parse prior to version 5.9.2 fails to reject out-of-bounds indices. Specially-crafted payloads can exploit this to cause devalue to alternate between different array representations, resulting in work that is quadratic with payload size.

Applications are potentially affected if they call devalue.parse with untrusted data.

Patches

The bug is fixed in devalue@5.9.2.

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.

Summary

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 ArrayBuffer hydration expecting base64 encoded strings as input, but not checking the assumption before decoding the input.

Details

The parser's ArrayBuffer hydration logic does not properly validate input before processing. Specially crafted inputs can cause disproportionate memory allocation or CPU usage on the receiving system.

Impact

This is a denial of service vulnerability affecting systems that use devalue.parse to handle data from potentially untrusted sources.

Affected systems should upgrade to patched versions immediately.

In devalue v5.6.3, 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.

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.