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SvelteKit CVE-2026-82257

| EUVDEUVD-2026-67583 MEDIUM
Improperly Controlled Modification of Object Prototype Attributes (Prototype Pollution) (CWE-1321)
2026-08-28 VulnCheck GHSA-6mgf-42wv-8j7p
Information Disclosure Prototype Pollution Kit
5.3
CVSS 4.0 · Vendor: VulnCheck
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Severity by source

Vendor (VulnCheck) PRIMARY
5.3 MEDIUM
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
vuln.today AI
3.7 LOW

Network vector confirmed, but AC:H reflects the three mandatory co-conditions (remote forms, file input, user-controlled paths); no privileges required for the attacker; impact limited to low availability.

3.1 AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L
4.0 AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N

Primary rating from Vendor (VulnCheck).

CVSS VectorVendor: VulnCheck

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
P
Scope
X

Lifecycle Timeline

3
Patch available
Aug 28, 2026 - 13:17 EUVD
Source Code Evidence Fetched
Aug 28, 2026 - 12:14 vuln.today
Analysis Generated
Aug 28, 2026 - 12:14 vuln.today

Blast Radius

ecosystem impact
† from your stack dependencies † transitive graph · vuln.today resolves 4-path depth
  • 1 npm packages depend on @sveltejs/kit (1 direct, 0 indirect)

Ecosystem-wide dependent count for version 2.69.1.

DescriptionCVE.org

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.

AnalysisAI

Prototype pollution in SvelteKit's remote form functions allows network-accessible attackers to remove methods from JavaScript object prototypes by supplying crafted, user-controlled file input path names. Affected versions are all @sveltejs/kit releases up to and including 2.69.0; the vendor released a fix in 2.69.1. …

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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata

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Vulnerability AssessmentAI

Exploitation Exploitation requires all three of the following conditions to be true simultaneously in the target application: (1) the application uses SvelteKit's remote form functions feature, (2) the form includes an input field of type 'file', and (3) the application accepts arbitrary user-controlled string values as the path name for that file field without sanitisation or allowlist validation. … Additional conditions and limiting factors are described in the full assessment.
Risk Assessment The provided CVSS 4.0 base vector (AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:L) scores 5.3, indicating medium severity with network reachability, low attack complexity, no privilege requirement, and only low availability impact on the vulnerable system with no subsequent-system impact. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in.
Exploit Scenario Full exploit scenario with step-by-step reproduction available after sign-in.
Remediation Upgrade @sveltejs/kit to version 2.69.1 or later; this is the vendor-released patch as confirmed by GitHub security advisory GHSA-866w-xmhq-wj7x (https://github.com/sveltejs/kit/security/advisories/GHSA-866w-xmhq-wj7x) and implemented via pull request #16218 and commit df32f6fe86cdd0b68b650e3e4631e5896453dcd3. … Detailed patch versions, workarounds, and compensating controls in full report.
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Same technique Information Disclosure

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CVE-2026-82257 vulnerability details – vuln.today
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