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MEDIUM severity

SvelteKit: Prototype pollution in file input deletion path in remote-function formsGHSA-866w-xmhq-wj7x

MEDIUMFix: sveltejs/kit#16218

GHSA-866w-xmhq-wj7x is a medium-severity (CVSS 4.3) CWE-1321 vulnerability in @sveltejs/kit. A fix is available for @sveltejs/kit — see the affected versions and patch details below.

Also known asCVE-2026-82257
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
None indexed
Exploitation data as of Oct 23, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

  • CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for GHSA-866w-xmhq-wj7x.

EPSS Exploitation Probability

via FIRST.org ↗
0.4%probability of exploitation in next 30 days
Lower Risk+0.15%
Lower risk than most CVEs28th percentile — riskier than 28% of all scored CVEsHighest risk
0.00%0.29%0.57%0.86%0.2%0.4%Sep 26Oct 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

GHSA-866w-xmhq-wj7x by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 394,803 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

1 pkg affected

How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.

216other npm packages depend on this — each one inherits the vulnerability until it's patched upstream
@sveltejs/kitnpm
2.2Mdownloads / week

Description

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.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
📦npm@sveltejs/kitall versions2.69.1npm install @sveltejs/kit@2.69.1

Affected Products

1 product · 1 configurations
Application
sveltekitsvelte
< 2.69.1
range

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @sveltejs/kit, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update @sveltejs/kit to 2.69.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-866w-xmhq-wj7x is resolved across your whole dependency graph.

  3. Workarounds

    If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Frequently Asked Questions

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.
O3 Security · Impact-Aware SCA

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