GHSA-866w-xmhq-wj7x: SvelteKit Prototype Pollution Vulnerability

MODERATE
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CVSS 4.3
CWE-1321
Published
Advisory Summary

GHSA-866w-xmhq-wj7x is a MODERATE (CVSS 4.3) prototype pollution vulnerability (CWE-1321: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')) affecting SvelteKit libraries in the npm ecosystem. The issue involves prototype pollution in file input deletion path in remote-function forms. Remediation is available by upgrading affected packages to version 2.69.1.

GHSA-866w-xmhq-wj7x at a Glance

CVE Identifier N/A
GHSA Identifier GHSA-866w-xmhq-wj7x
Severity MODERATE
CVSS v3.1 Base Score 4.3
CWE Classification CWE-1321: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')
Affected Product SvelteKit
Package Ecosystem npm
Published Date
Last Updated

Security Impact

CVSS: 4.3

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction Required (UI:R)
Scope Unchanged (S:U)
Confidentiality None (C:N)
Integrity None (I:N)
Availability Low (A:L)

How to Fix GHSA-866w-xmhq-wj7x

To remediate this vulnerability, upgrade all affected SvelteKit dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

@sveltejs/kit fixed: 2.69.1 
npm install @sveltejs/kit@2.69.1
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

npm ls @sveltejs/kit

How to Check if You Are Affected

To determine whether your Node.js application is affected by GHSA-866w-xmhq-wj7x, inspect your project dependencies using npm:

npm ls @sveltejs/kit

Analyze the terminal output to locate any version of SvelteKit in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 2.69.1), your application is affected.

Note: The npm ls @sveltejs/kit command inspects dependencies declared in your package.json and lockfile; it does not perform automated runtime dynamic scanning.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-1321: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution'), where the product receives input from an upstream component that specifies attributes that are to be initialized or updated in an object, but it does not properly control modifications of attributes of the object prototype. In SvelteKit, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

If you use remote form functions, have an input field of type `file`, and accept arbitrary user-controlled path names for the field, then you are vulnerable to a prototype pollution attack where the attacker can remove e.g. methods on the prototype.

GHSA-866w-xmhq-wj7x Affected SvelteKit Versions

1 component(s)
Fixed Versions:
2.69.1
Product / Package Ecosystem Affected Versions Fixed Version
@sveltejs/kit
npm/@sveltejs/kit
npm
< 2.69.1
2.69.1

References

GitHub Advisory / Wiki ADVISORY
https://github.com/sveltejs/kit/security/advisories/GHSA-866w-xmhq-wj7x
SvelteKit Source Repository REPOSITORY
https://github.com/sveltejs/kit/pull/16218
Security Fix Commit FIX COMMIT
https://github.com/sveltejs/kit/commit/df32f6fe86cdd0b68b650e3e4631e5896453dcd3
SvelteKit Source Repository REPOSITORY
https://github.com/sveltejs/kit
SvelteKit Release RELEASE
https://github.com/sveltejs/kit/releases/tag/@sveltejs/kit@2.69.1
SvelteKit Release RELEASE
https://github.com/sveltejs/kit/releases/tag/@sveltejs/kit@3.0.0-next.7

Frequently Asked Questions

What is GHSA-866w-xmhq-wj7x?
GHSA-866w-xmhq-wj7x is a security vulnerability in SvelteKit involving Prototype pollution in file input deletion path in remote-function forms under CWE-1321: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution').
Which SvelteKit versions are affected?
Affected versions include releases prior to 2.69.1 across affected packages: @sveltejs/kit.
What version fixes GHSA-866w-xmhq-wj7x?
Upgrading to 2.69.1 (or the latest patched release for your respective branch) resolves the vulnerability.
Is @sveltejs/kit affected?
Yes, @sveltejs/kit is affected in releases prior to 2.69.1. Upgrade your dependency to 2.69.1 or later.
What is the CVSS score of GHSA-866w-xmhq-wj7x?
GHSA-866w-xmhq-wj7x has a CVSS v3.1 base score of 4.3 (MODERATE) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L.
What CWE is associated with GHSA-866w-xmhq-wj7x?
GHSA-866w-xmhq-wj7x is classified under CWE-1321: Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution') (The product receives input from an upstream component that specifies attributes that are to be initialized or updated in an object, but it does not properly control modifications of attributes of the object prototype.).
How can I check npm dependencies for GHSA-866w-xmhq-wj7x?
Run the dependency tree command: 'npm ls @sveltejs/kit'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-866w-xmhq-wj7x",
  "modified" : "2026-07-24T15:58:05Z",
  "published" : "2026-07-24T15:58:05Z",
  "aliases" : [ ],
  "summary" : "SvelteKit: Prototype pollution in file input deletion path in remote-function forms",
  "details" : "If you use remote form functions, have an input field of type `file`, and accept arbitrary user-controlled path names for the field, then you are vulnerable to a prototype pollution attack where the attacker can remove e.g. methods on the prototype.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "@sveltejs/kit"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "2.69.1"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 2.69.0"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/sveltejs/kit/security/advisories/GHSA-866w-xmhq-wj7x"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/sveltejs/kit/pull/16218"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/sveltejs/kit/commit/df32f6fe86cdd0b68b650e3e4631e5896453dcd3"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/sveltejs/kit"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/sveltejs/kit/releases/tag/@sveltejs/kit@2.69.1"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/sveltejs/kit/releases/tag/@sveltejs/kit@3.0.0-next.7"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-1321" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-07-24T15:58:05Z",
    "nvd_published_at" : null
  }
}