# CVE-2026-82259: SvelteKit 2.49.0 before 2.53.3 Denial of Service via form

> Attackers can cause denial of service in SvelteKit applications by exploiting deserialization expansion in experimental remote form functions.

- **Severity:** High 8.7 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 28 Aug 2026
- **Updated:** 8 Oct 2026
- **Also known as:** GHSA-7jhg-723h-fjhx, GHSA-fpg4-jhqr-589c

## What is CVE-2026-82259?

CVE-2026-82259 is a high-severity denial of service vulnerability in sveltejs kit, published on 28 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

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.

Weakness: CWE-502 (Deserialization of Untrusted Data)

## Which versions are affected by CVE-2026-82259?

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


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `@sveltejs/kit` | npm | From 2.49.0 | 2.53.3 |
| `@sveltejs/kit` | npm | From 2.49.0 | 2.53.3 |

Products: Svelte Sveltekit.

## How do I fix CVE-2026-82259?

Upgrade @sveltejs/kit to 2.53.3 or later.

## Is CVE-2026-82259 being exploited?

There is no known exploitation of CVE-2026-82259 in the wild and no public exploit code.

## Other vulnerabilities in sveltejs kit

- [CVE-2023-29008](https://insights.sbomify.com/CVE-2023-29008/): SvelteKit framework has Insufficient CSRF protection for CORS requests (high 8.8)
- [CVE-2023-29003](https://insights.sbomify.com/CVE-2023-29003/): SvelteKit has Insufficient Cross-Site Request Forgery Protection (high 8.8)
- [CVE-2026-82260](https://insights.sbomify.com/CVE-2026-82260/): SvelteKit before 2.52.2 Memory Exhaustion via Remote Form Deserialization (high 8.7)
- [CVE-2026-82261](https://insights.sbomify.com/CVE-2026-82261/): SvelteKit before 2.52.2 CPU Exhaustion via Remote Form Deserialization (high 8.7)
- [CVE-2026-82256](https://insights.sbomify.com/CVE-2026-82256/): SvelteKit before 2.69.1 Denial of Service via Remote Form (medium 6.9)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-82259 and fix it if it is affected.

What it is: CVE-2026-82259 is a high-severity denial of service vulnerability in sveltejs kit, published on 28 Aug 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-2026-82259 in the wild and no public exploit code.

Affected packages and fixed versions:
- @sveltejs/kit (npm): affected from 2.49.0; fixed in 2.53.3
- @sveltejs/kit (npm): affected from 2.49.0; fixed in 2.53.3

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-2026-82259/ (Markdown: https://insights.sbomify.com/CVE-2026-82259/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-82259
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-82259
- OSV: https://osv.dev/vulnerability/CVE-2026-82259

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-82259/
Summaries are generated and may contain mistakes; the official description above is the record.