What is CVE-2026-82257?

CVE-2026-82257 is a medium-severity vulnerability in Sveltejs Kit, 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.

Prototype Pollution in Sveltejs Kit

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

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.

Affected products

Sveltejs Kit

Weakness classification (CWE)

CWE-1321 — Improperly Controlled Modification of Object Prototype Attributes (Prototype Pollution)

References

disclosure@vulncheck.com (vendor-advisory)
disclosure@vulncheck.com (third-party-advisory)

Frequently asked questions

What is CVE-2026-82257?: CVE-2026-82257 is a medium-severity vulnerability in Sveltejs Kit, 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.