Is CVE-2026-22803 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-22803 being exploited in the wild.

How severe is CVE-2026-22803?

Medium severity, with a CVSS score of 4, published 15 January 2026.

Which products and versions are affected?

@sveltejs/kit (npm) SEMVER:introduced=2.49.0,fixed=2.49.5.

Is there a fix for CVE-2026-22803?

Yes. @sveltejs/kit (npm): upgrade to 2.49.5 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

How is CVE-2026-22803 attacked?

It is attacked over the network, in a software library.

Am I affected by CVE-2026-22803?

Check whether you run @sveltejs/kit (npm) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-22803: SvelteKit memory amplification DoS in form deserializer

CVE-2026-22803 · Severity: medium · CVSS 4 · Published 2026-01-15

SvelteKit is a JavaScript framework for building web applications. When the experimental remote functions feature is enabled, attackers can exploit a flaw in how form data is deserialized to allocate large amounts of server memory by sending specially crafted requests and stalling the connection. This can exhaust the server's memory and cause the application to become unavailable.

Technologies: @sveltejs/kit (npm). Vendors: npm.

Quick answers

Is CVE-2026-22803 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-22803 being exploited in the wild.
How severe is CVE-2026-22803?: Medium severity, with a CVSS score of 4, published 15 January 2026.
Which products and versions are affected?: @sveltejs/kit (npm) SEMVER:introduced=2.49.0,fixed=2.49.5.
Is there a fix for CVE-2026-22803?: Yes. @sveltejs/kit (npm): upgrade to 2.49.5 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-22803 attacked?: It is attacked over the network, in a software library.
Am I affected by CVE-2026-22803?: Check whether you run @sveltejs/kit (npm) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

@sveltejs/kit (npm): upgrade to 2.49.5 or later
```
npm install @sveltejs/kit@2.49.5
```

Technical details

This vulnerability is a memory amplification DoS in the binary form deserializer for SvelteKit's experimental remote functions feature (application/x-sveltekit-formdata). When a form is submitted, the client encodes data in a custom format; the first 8 bytes specify the expected data length. If the request body is not yet available, SvelteKit eagerly allocates an array buffer of that size. An unauthenticated attacker can exploit this by sending the 8-byte header with a large data_length value, then stalling the connection to hold that allocation indefinitely. Repeated connections exhaust server memory, causing denial of service. The vulnerability affects SvelteKit versions 2.49.0 through 2.49.4 with experimental.remoteFunctions enabled and is fixed in version 2.49.5.

Affected products

SvelteJS SvelteKit 2.49.0 to 2.49.4

Identifiers

CVE-2026-22803
GHSA-j2f3-wq62-6q46

Timeline

2026-01-15: disclosed: GHSA-j2f3-wq62-6q46 and CVE-2026-22803 published
2026-01-15: patched: Fixed in @sveltejs/kit 2.49.5 and @sveltejs/adapter-node 5.5.1

References

https://github.com/sveltejs/kit/security/advisories/GHSA-j2f3-wq62-6q46

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