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 (@sveltejs/kit) from 2.10.0 before 3.0.0 contains a path traversal vulnerability in the vite preview server on Windows that allows unauthenticated attackers to read files outside the prerendered output directory. Attackers who can reach the preview server through network access or a tunnel can send crafted requests to expose source code, configuration, or credentials readable by the server process.

SvelteKit before 3.0.0 contains a server-side request forgery vulnerability because self-fetch fallbacks follow HTTP redirects automatically. Attackers can manipulate the Host or forwarded headers to point fallback requests at their server, which redirects them to internal services.

SvelteKit (@sveltejs/kit) before 3.0.0 contains a cross-site scripting vulnerability in prerendered pages because a cache-control header value set via setHeaders is inserted without escaping into a <meta http-equiv="cache-control"> tag. An attacker who can influence that untrusted value at prerender time can break out of the content attribute and inject HTML or JavaScript that executes when users visit the page.

SvelteKit (@sveltejs/kit) before 3.0.0 contains an open redirect vulnerability in enhanced form actions (use:enhance) on routes accepting paths beginning with a double slash. Attackers can craft action paths starting with // that become protocol-relative URLs, causing non-redirect form results to navigate victims to attacker-controlled sites.

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.