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CVE-2026-40074: SvelteKit's invalidated redirect in handle hook causes Denial-of-Service

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-04-10 · updated 2026-10-26
• Weakness: CWE-755

Description

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.

Affected products

• Svelte Kit: before 2.57.1 — fixed in 2.57.1

How to fix

Upgrade to a fixed version: Svelte Kit 2.57.1. Check the vendor advisory for mitigations.

References

• https://github.com/sveltejs/kit/commit/10d7b44425c3d9da642eecce373d0c6ef83b4fcd
• https://github.com/sveltejs/kit/releases/tag/@sveltejs/kit@2.57.1
• https://github.com/sveltejs/kit/security/advisories/GHSA-3f6h-2hrp-w5wx

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