Vulnerability · Published Aug 28, 2026 · Assigned by VulnCheck

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

High 7.5

In plain English

A high-severity unsafe deserialization in kit from sveltejs. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 45% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)7.5High

Exploit odds (30 days)0.5%top 54.8% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

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.

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
npm	@sveltejs/kit	2.53.3	GHSA-fpg4-jhqr-589c

Affected products (as reported)

Vendor	Product	Versions
sveltejs	kit	2.49.0 – before 2.53.3

Weakness: CWE-502 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

References

GitHub Security Advisory (GHSA-fpg4-jhqr-589c) vendor-advisory
VulnCheck Advisory: SvelteKit 2.49.0 before 2.53.3 Denial of Service via form third-party-advisory