CVE-2026-82257: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution') in sveltejs kit
Description
SvelteKit versions before 2.69.1 have a prototype pollution vulnerability in remote form functions that handle file input fields with user-controlled path names. This flaw allows attackers to manipulate the deletion path to remove methods on the prototype, which can disable application functionality. The vulnerability has a CVSS 4.0 base score of 5.3, indicating medium severity.
CVSS v4.0
Score 5.3medium
Affected software
sveltejs
kit
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
CVE-2026-82257 is a prototype pollution vulnerability affecting SvelteKit versions prior to 2.69.1. It arises in remote form functions that accept file input fields with arbitrary user-controlled path names. An attacker can exploit this by manipulating the deletion path to remove methods on the JavaScript object prototype, potentially disrupting application behavior or functionality.
Potential Impact
The vulnerability allows attackers to modify prototype attributes by deleting prototype methods, which can lead to disabling application functionality. The CVSS score of 5.3 (medium severity) reflects the potential for limited impact without requiring privileges or user interaction beyond form submission.
Mitigation Recommendations
Upgrade SvelteKit to version 2.69.1 or later, where this prototype pollution vulnerability is fixed. Patch status is confirmed by the affectedVersions field indicating versions before 2.69.1 are vulnerable.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- VulnCheck
- Date Reserved
- 2026-08-28T10:39:30.356Z
- Cvss Version
- 4.0
- State
- PUBLISHED
Threat ID: 6a916f93acd9273b49cf92fa
Added to database: 08/28/2026, 11:22:59 UTC
Last enriched: 10/09/2026, 21:23:31 UTC
Last updated: 10/12/2026, 06:48:19 UTC
Views: 91
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