Prototype Pollution in Svelte Sveltekit
CVE-2026-82257
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.
Vulnerability class: Prototype Pollution
Published · last modified .
CVSS v3 metric
CVSS v3 base score 4.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L.
EPSS exploit prediction
EPSS: 0.004 (27.6th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 28th percentile — 27.6% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.002 · newest: 0.004 · change: +0.002
Affected products
Weakness classification (CWE)
References
- github.com/sveltejs/kit/security/advisories/GHSA-866w-xmhq-wj7x (vendor-advisory, Vendor Advisory)
- www.vulncheck.com/advisories/sveltekit-before-2.69.1-prototype-pollution-via-fi… (Third Party Advisory, third-party-advisory)
Frequently asked questions
- What is CVE-2026-82257?
- CVE-2026-82257 is a medium-severity vulnerability in Svelte Sveltekit, classified under Improperly Controlled Modification of Object Prototype Attributes (Prototype Pollution). CVSS score: 4.3/10. Published 2026-08-28.
- How severe is CVE-2026-82257?
- Medium severity. CVSS v3 base score is 4.3 out of 10.