Deserialization in Svelte Sveltekit
CVE-2026-82259
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.
Vulnerability class: Insecure Deserialization
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
EPSS exploit prediction
EPSS: 0.005 (43.4th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 43rd percentile — 43.4% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.004 · newest: 0.005 · change: +0.002
Affected products
Weakness classification (CWE)
References
- github.com/sveltejs/kit/security/advisories/GHSA-fpg4-jhqr-589c (vendor-advisory, Vendor Advisory)
- www.vulncheck.com/advisories/sveltekit-2.49.0-before-2.53.3-denial-of-service-v… (Third Party Advisory, third-party-advisory)
Frequently asked questions
- What is CVE-2026-82259?
- CVE-2026-82259 is a high-severity vulnerability in Svelte Sveltekit, classified under Deserialization of Untrusted Data. CVSS score: 7.5/10. Published 2026-08-28.
- How severe is CVE-2026-82259?
- High severity. CVSS v3 base score is 7.5 out of 10.