CVE-2026-82258

SvelteKit versions 2.49.0 through 2.49.4 contain a vulnerability in the experimental form remote function, which uses a binary data format for submitted form data. A specially crafted payload can cause the server to allocate a large amount of memory, leading to DoS via memory exhaustion. The vulnerability is fixed in version 2.49.5.

SvelteKit prior to 2.49.5 is vulnerable to server side request forgery (SSRF) and denial of service (DoS) under certain conditions. From 2.44.0 through 2.49.4, the vulnerability results in a DoS when your app has at least one prerendered route. From 2.19.0 through 2.49.4, the vulnerability results in a DoS when your app has at least one prerendered route and you are using adapter-node without a configured ORIGIN environment variable, and you are not using a reverse proxy that implements Host header validation. This vulnerability is fixed in 2.49.5.

SvelteKit versions from 2.49.0 to 2.52.1 with experimental remote functions and forms enabled contain a CPU exhaustion vulnerability in form deserialization. An attacker can send malformed form data to cause the server to become unresponsive while processing the request, resulting in denial of service. Fixed in 2.52.2.

SvelteKit versions from 2.49.0 to 2.52.1 with experimental remote functions and forms enabled contain a memory exhaustion vulnerability in remote form deserialization. Malformed form data can cause excessive memory allocation, crashing the server process and resulting in denial of service. Fixed in 2.52.2.

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 before 2.69.1 contain a prototype pollution vulnerability in remote form functions with file input fields that accept arbitrary user-controlled path names. Attackers can manipulate the deletion path to remove methods on the prototype, potentially disabling application functionality.

SvelteKit before 2.69.1 fails to properly validate remote form function payload sizes, allowing attackers to crash the Node process by sending large payloads. Repeated exploitation causes denial of service by repeatedly crashing the application process.

SvelteKit is a framework for rapidly developing robust web applications using Svelte. Prior to 2.70.2, the content negotiation header parser uses a regular expression vulnerable to quadratic backtracking, so a maliciously crafted header value can cause excessive CPU consumption and degrade or deny service. Version 2.70.2 fixes the issue.