GHSA-866w-xmhq-wj7x CVE-2026-82257
SvelteKit: Prototype pollution in file input deletion path in remote-function forms
- Severity
- 5.3 / 10
- Medium · CVSS 4.0
- Exploit chance (EPSS)
- 0.36%
- Chance of exploitation in the next 30 days. Higher than 29.52% of scored vulnerabilities.
- Known exploited
- No
- Not in CISA's catalog
- Weakness
- CWE-1321 Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')
- Fix
2.69.1- Upgrade @sveltejs/kit to this version or later
Description
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.
Affected versions
npm
| Package | Vulnerable | Fixed in |
|---|---|---|
| @sveltejs/kit | < 2.69.1 |
2.69.1 |
How to fix
Move to the fixed version or later with your package manager, update the lockfile, and run your tests. If the package only arrives through another dependency, upgrade that dependency first. If none of its releases pulls a fixed version yet, force the version with your package manager's override.
@sveltejs/kit npm → 2.69.1
- npm
npm install @sveltejs/kit@2.69.1- yarn
yarn add @sveltejs/kit@2.69.1- pnpm
pnpm add @sveltejs/kit@2.69.1
Severity breakdown
CVSS 4.0 5.3
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
- Attack vector
- Network
- Attack complexity
- Low
- Attack requirements
- None
- Privileges required
- None
- User interaction
- Passive
- Confidentiality (vulnerable system)
- None
- Integrity (vulnerable system)
- None
- Availability (vulnerable system)
- Low
- Confidentiality (subsequent systems)
- None
- Integrity (subsequent systems)
- None
- Availability (subsequent systems)
- None
- Exploit maturity
- Not defined
- Scope
- X
CVSS 3.1 4.3
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L
- Attack vector
- Network
- Attack complexity
- Low
- Privileges required
- None
- User interaction
- Required
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- Low
Weakness
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 to prevent it
- Implementation: By freezing the object prototype first (for example, Object.freeze(Object.prototype)), modification of the prototype becomes impossible.
- Architecture and Design: By blocking modifications of attributes that resolve to object prototype, such as proto or prototype, this weakness can be mitigated.
- Implementation: When handling untrusted objects, validating using a schema can be used.
- Implementation: By using an object without prototypes (via Object.create(null) ), adding object prototype attributes by accessing the prototype via the special attributes becomes impossible, mitigating this weakness.
- Implementation: Map can be used instead of objects in most cases. If Map methods are used instead of object attributes, it is not possible to access the object prototype or modify it.
References
Advisories
Packages
Other links
Timeline
- Published
- Last updated by the source
- Latest EPSS score
Related advisories
| Advisory | Severity | Why it's related |
|---|---|---|
| GHSA-27mw-82g8-phjj SvelteKit : XSS via untrusted cache-control header in prerendered page | Low | Also affects @sveltejs/kit |
| GHSA-pfhg-q3qv-9q6r SvelteKit: URL redirection to untrusted site via enhanced form submission | Medium | Also affects @sveltejs/kit |
| GHSA-29g2-3rmr-qm68 SvelteKit: ReDoS (O(n^2)) in content negotiation — unauthenticated DoS via the Accept header | Medium | Also affects @sveltejs/kit |
| GHSA-wqjv-9729-c5q2 SvelteKit: Big remote form function payloads can cause Node process to crash | Medium | Also affects @sveltejs/kit |
| GHSA-hgv7-v322-mmgr @sveltejs/kit: `query.batch` cross-talk | Medium | Also affects @sveltejs/kit |
| GHSA-3f6h-2hrp-w5wx @sveltejs/kit: Unvalidated redirect in handle hook causes Denial-of-Service | High | Also affects @sveltejs/kit |
| GHSA-2crg-3p73-43xp @sveltejs/adapter-node has a BODY_SIZE_LIMIT bypass | High | Also affects @sveltejs/kit |
| GHSA-fpg4-jhqr-589c SvelteKit has deserialization expansion in unvalidated `form` remote function leading to Denial of Service (experimental only) | High | Also affects @sveltejs/kit |
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