SvelteKit versions from 2.49.0 through 2.53.2 (fixed in 2.53.3) contain a deserialization expansion issue in the experimental form remote function. When an application enables experimental.remoteFunctions and uses the form function to process the files array without validating files.length or individual file sizes, an attacker can submit relatively small inputs that expand into very large file arrays, leading to expensive processing and denial of service.

SvelteKit versions 2.49.0 through 2.53.2 contain a deserialization expansion vulnerability in the experimental form remote function. When applications enable experimental.remoteFunctions and use the form function to process file arrays without validating files.length or individual file sizes, attackers can exploit this to cause denial of service. An attacker submits relatively small inputs that expand into very large file arrays, leading to expensive server-side processing. The vulnerability is fixed in SvelteKit version 2.53.3. Applications not using experimental.remoteFunctions or the form function are not affected. The issue is classified as a denial-of-service risk due to unbounded deserialization expansion.