Svelte vulnerabilities

CVE-2026-82261 High · 7.5 CWE-400 Aug 28, 2026

SvelteKit before 2.52.2 CPU Exhaustion via Remote Form Deserialization

SvelteKit (@sveltejs/kit) versions >=2.49.0 and <=2.52.1 with experimental remote functions and form 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.

CVE-2026-82260 High · 7.5 CWE-400 Aug 28, 2026

SvelteKit before 2.52.2 Memory Exhaustion via Remote Form Deserialization

SvelteKit (@sveltejs/kit) versions >=2.49.0 and <=2.52.1 with experimental remote functions (experimental.remoteFunctions) and form 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.

CVE-2026-82259 High · 7.5 CWE-502 Aug 28, 2026

SvelteKit 2.49.0 before 2.53.3 Denial of Service via form

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.

CVE-2026-82258 Medium · 4.8 CWE-362 Aug 28, 2026

SvelteKit 2.38.0 before 2.60.1 Cross-User Data Disclosure via query.batch

SvelteKit versions from 2.38.0 before 2.60.1 contain a race condition in query.batch that allows concurrent requests from different users to merge under a single request context. Attackers can exploit specific timing conditions to access sensitive data from other users' concurrent requests.

CVE-2026-82257 Medium · 4.3 CWE-1321 Aug 28, 2026

SvelteKit before 2.69.1 Prototype Pollution via File Input

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.

CVE-2026-82256 Medium · 5.3 CWE-400 Aug 28, 2026

SvelteKit before 2.69.1 Denial of Service via Remote Form

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.

CVE-2026-42599 Medium · 6.1 CWE-79 Jun 9, 2026

Cross-site scripting via spread attributes in Svelte SSR

Svelte is a performance oriented web framework. Prior to version 5.55.7, when using spread syntax to render attributes from untrusted data, event handler properties are included in the rendered HTML output. If an application spreads user-controlled or external data as element attributes, an attacker can inject malicious event handlers that execute in victims' browsers. Note that this vulnerability only triggers if the user's browser has JavaScript enabled but Svelte's hydration mechanism does not reach the vulnerable element before the event fires. This issue has been patched in version 5.55.7.

CVE-2026-42573 Medium · 6.1 CWE-79 Jun 9, 2026

Svelte: XSS via DOM Clobbering of Internal Framework State

Svelte is a performance oriented web framework. Prior to version 5.55.7, Svelte was vulnerable to DOM clobbering of its internal framework state on elements, potentially leading to XSS attacks. This issue has been patched in version 5.55.7.

CVE-2026-42570 High · 7.5 CWE-770 Jun 9, 2026

Svelte devalue: DoS via sparse array deserialization

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.

CVE-2026-42567 High · 7.5 CWE-1333 Jun 9, 2026

Svelte: ReDoS in `<svelte:element>` Tag Validation

Svelte is a performance oriented web framework. From version 5.51.5 to before version 5.55.7, an internal regex in the Svelte runtime can take exponential time to test in <svelte:element this={tag}></svelte:element>. This issue has been patched in version 5.55.7.

CVE-2026-40074 High · 7.5 CWE-755 Apr 10, 2026

SvelteKit's invalidated redirect in handle hook causes Denial-of-Service

SvelteKit is a framework for rapidly developing robust, performant web applications using Svelte. Prior to 2.57.1, redirect, when called from inside the handle server hook with a location parameter containing characters that are invalid in a HTTP header, will cause an unhandled TypeError. This could result in DoS on some platforms, especially if the location passed to redirect contains unsanitized user input. This vulnerability is fixed in 2.57.1.

CVE-2026-40073 High · 7.5 CWE-770 Apr 10, 2026

SvelteKit has a BODY_SIZE_LIMIT bypass in @sveltejs/adapter-node

SvelteKit is a framework for rapidly developing robust, performant web applications using Svelte. Prior to 2.57.1, under certain circumstances, requests could bypass the BODY_SIZE_LIMIT on SvelteKit applications running with adapter-node. This bypass does not affect body size limits at other layers of the application stack, so limits enforced in the WAF, gateway, or at the platform level are unaffected. This vulnerability is fixed in 2.57.1.

CVE-2026-30226 High · 7.5 CWE-1321 Mar 11, 2026

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

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.

CVE-2026-27902 Medium · 5.4 CWE-79 Feb 25, 2026

Svelte Vulnerable to XSS via HTML Comment Injection in SSR Error Boundary Hydration Markers

Svelte performance oriented web framework. Prior to version 5.53.5, errors from `transformError` were not correctly escaped prior to being embedded in the HTML output, causing potential HTML injection and XSS if attacker-controlled content is returned from `transformError`. Version 5.53.5 fixes the issue.

CVE-2026-27901 Medium · 6.1 CWE-79 Feb 25, 2026

Svelte vulnerable to XSS during SSR with contenteditable `bind:innerText` and `bind:textContent`

Svelte performance oriented web framework. Prior to version 5.53.5, the contents of `bind:innerText` and `bind:textContent` on `contenteditable` elements were not properly escaped. This could enable HTML injection and Cross-Site Scripting (XSS) if rendering untrusted data as the binding's initial value on the server. Version 5.53.5 fixes the issue.

CVE-2026-27125 Medium · 6.8 CWE-915 Feb 20, 2026

Svelte SSR attribute spreading includes inherited properties from prototype chain

svelte performance oriented web framework. Prior to 5.51.5, in server-side rendering, attribute spreading on elements (e.g. <div {...attrs}>) enumerates inherited properties from the object's prototype chain rather than only own properties. In environments where Object.prototype has already been polluted — a precondition outside of Svelte's control — this can cause unexpected attributes to appear in SSR output or cause SSR to throw errors. Client-side rendering is not affected. This vulnerability is fixed in 5.51.5.

CVE-2026-27122 Medium · 5.4 CWE-79 Feb 20, 2026

Svelte SSR does not validate dynamic element tag names in `<svelte:element>`

svelte performance oriented web framework. Prior to 5.51.5, when using <svelte:element this={tag}> in server-side rendering, the provided tag name is not validated or sanitized before being emitted into the HTML output. If the tag string contains unexpected characters, it can result in HTML injection in the SSR output. Client-side rendering is not affected. This vulnerability is fixed in 5.51.5.

CVE-2026-27121 Medium · 5.4 CWE-79 Feb 20, 2026

Svelte affected by cross-site scripting via spread attributes in Svelte SSR

svelte performance oriented web framework. Versions of svelte prior to 5.51.5 are vulnerable to cross-site scripting (XSS) during server-side rendering. When using spread syntax to render attributes from untrusted data, event handler properties are included in the rendered HTML output. If an application spreads user-controlled or external data as element attributes, an attacker can inject malicious event handlers that execute in victims' browsers. This vulnerability is fixed in 5.51.5.

CVE-2026-27119 Medium · 5.4 CWE-79 Feb 20, 2026

Svelte affected by XSS in SSR `<option>` element

svelte performance oriented web framework. From 5.39.3, <=5.51.4, in certain circumstances, the server-side rendering output of an <option> element does not properly escape its content, potentially allowing HTML injection in the SSR output. Client-side rendering is not affected. This vulnerability is fixed in 5.51.5.

CVE-2025-15265 Medium · 6.1 CWE-79 Jan 15, 2026

Svelte 5.46.0 - Hydratable Key Script-Breakout XSS (SSR)

An SSR XSS exists in async hydration when attacker‑controlled keys are passed to hydratable. The key is embedded inside a <script> block without HTML‑safe escaping, allowing </script> to terminate the script and inject arbitrary JavaScript. This enables remote script execution in users' browsers, with potential for session theft and account compromise. This issue affects Svelte: from 5.46.0 before 5.46.3.

CVE-2026-22803 High · 7.5 CWE-770 Jan 15, 2026

SvelteKit has a memory amplification DoS in Remote Functions binary form deserializer

SvelteKit is a framework for rapidly developing robust, performant web applications using Svelte. From 2.49.0 to 2.49.4, the experimental form remote function uses a binary data format containing a representation of submitted form data. A specially-crafted payload can cause the server to allocate a large amount of memory, causing DoS via memory exhaustion. This vulnerability is fixed in 2.49.5.

CVE-2026-22775 High · 7.5 CWE-405 Jan 15, 2026

devalue vulnerable to denial of service due to memory/CPU exhaustion in devalue.parse

Svelte devalue is a JavaScript library that serializes values into strings when JSON.stringify isn't sufficient for the job. From 5.1.0 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 ArrayBuffer hydration expecting base64 encoded strings as input, but not checking the assumption before decoding the input. This vulnerability is fixed in 5.6.2.

CVE-2026-22774 High · 7.5 CWE-405 Jan 15, 2026

devalue vulnerable to denial of service due to memory exhaustion in devalue.parse

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.

CVE-2025-67647 Critical · 9.1 CWE-918 Jan 15, 2026

SvelteKit Denial of service and possible SSRF when using prerendering

SvelteKit is a framework for rapidly developing robust, performant web applications using Svelte. Prior to 2.49.5, SvelteKit is vulnerable to a 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 (export const prerender = true). 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.