# CVE-2026-82257: SvelteKit before 2.69.1 Prototype Pollution via File Input

> Attackers can cause denial of service in SvelteKit applications by exploiting prototype pollution in remote form file inputs.

- **Severity:** Medium 5.3 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 28 Aug 2026
- **Updated:** 8 Oct 2026
- **Also known as:** GHSA-6mgf-42wv-8j7p, GHSA-866w-xmhq-wj7x

## What is CVE-2026-82257?

CVE-2026-82257 is a medium-severity vulnerability in sveltejs kit, published on 28 Aug 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

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.

Weakness: CWE-1321 (Improperly Controlled Modification of Object Prototype Attributes)

## Which versions are affected by CVE-2026-82257?

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 | 2.69.1 |
| `@sveltejs/kit` | npm | All versions | 2.69.1 |

Products: Svelte Sveltekit.

## How do I fix CVE-2026-82257?

Upgrade @sveltejs/kit to 2.69.1 or later.

## Is CVE-2026-82257 being exploited?

There is no known exploitation of CVE-2026-82257 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-2026-82259](https://insights.sbomify.com/CVE-2026-82259/): SvelteKit 2.49.0 before 2.53.3 Denial of Service via form (high 8.7)
- [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)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-82257 and fix it if it is affected.

What it is: CVE-2026-82257 is a medium-severity vulnerability in sveltejs kit, published on 28 Aug 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2026-82257 in the wild and no public exploit code.

Affected packages and fixed versions:
- @sveltejs/kit (npm): affected all versions; fixed in 2.69.1
- @sveltejs/kit (npm): affected all versions; fixed in 2.69.1

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-2026-82257/ (Markdown: https://insights.sbomify.com/CVE-2026-82257/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-82257
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-82257
- OSV: https://osv.dev/vulnerability/CVE-2026-82257

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-82257/
Summaries are generated and may contain mistakes; the official description above is the record.