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

> Attackers can cause a Denial of Service in SvelteKit applications by triggering an unhandled TypeError via invalid characters in redirect locations within handle hooks.

- **Severity:** Medium 6.3 (`CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 10 Apr 2026
- **Updated:** 14 Apr 2026
- **Also known as:** GHSA-3f6h-2hrp-w5wx

## What is CVE-2026-40074?

CVE-2026-40074 is a medium-severity denial of service vulnerability in sveltejs kit, published on 10 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official 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.

Weakness: CWE-755 (Improper Handling of Exceptional Conditions)

## Which versions are affected by CVE-2026-40074?

2 open source packages ship an affected version, including @sveltejs/kit. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `@sveltejs/kit` | npm | All versions | 2.57.1 |
| `@sveltejs/kit` | npm | All versions | 2.57.1 |

Products: Svelte Kit.

## How do I fix CVE-2026-40074?

Upgrade @sveltejs/kit to 2.57.1 or later.

## Is CVE-2026-40074 being exploited?

There is no known exploitation of CVE-2026-40074 in the wild and no public exploit code.

## Other vulnerabilities in sveltejs kit

- [CVE-2026-40073](https://insights.sbomify.com/CVE-2026-40073/): SvelteKit has a BODY_SIZE_LIMIT bypass in @sveltejs/adapter-node (high 8.2)
- [CVE-2026-22803](https://insights.sbomify.com/CVE-2026-22803/): SvelteKit has a memory amplification DoS in Remote Functions binary form deserializer (high 8.2)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-40074 and fix it if it is affected.

What it is: CVE-2026-40074 is a medium-severity denial of service vulnerability in sveltejs kit, published on 10 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-40074 in the wild and no public exploit code.

Affected packages and fixed versions:
- @sveltejs/kit (npm): affected all versions; fixed in 2.57.1
- @sveltejs/kit (npm): affected all versions; fixed in 2.57.1

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-40074/ (Markdown: https://insights.sbomify.com/CVE-2026-40074/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-40074
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-40074
- OSV: https://osv.dev/vulnerability/CVE-2026-40074

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-40074/
Summaries are generated and may contain mistakes; the official description above is the record.