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Fencer Intel
high 7.5

CVE-2026-128120 json

SvelteKit: DoS while parsing form data from a remote functions `form`

published 16d ago modified yesterday also EUVD-2026-125732 , GHSA-3r8g-jcqq-3p5j

Unreviewed: the maintainers' own advisory

Published by the maintainers on their GitHub repository sveltejs/kit. GitHub has not reviewed it into the GitHub Advisory Database, so the affected packages and versions are the maintainers' word. Read the full advisory on GitHub.

cvss
7.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 28%
public exploits
0
none known

Summary

SvelteKit is a framework for rapidly developing robust, performant web applications using Svelte. From version 2.42.0 until 3.1.1, applications using the experimental remote functions flag and a remote form function could perform quadratic synchronous work while parsing a specially crafted request with many form entries. The parsing work could block the event loop for an extended period and deny service. This issue is fixed in 3.1.1.

Patch / fix

  • npm @sveltejs/kit 3.1.1

Is CVE-2026-128120 in your dependencies? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

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Exploit prediction

0.35% chance of exploitation in the next 30 days, higher than 28% of all scored CVEs (FIRST EPSS, 2026-11-14).

CVSS scores

assigned by version score vector
CNA 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected packages

ecosystem package affected fixed in
npm @sveltejs/kit
>=2.42.0, <=3.1.0
3.1.1

Affected products

  • sveltejs kit

Classification

Weakness
  • CWE-407 Inefficient Algorithmic Complexity

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

The maintainers of sveltejs/kit published their own advisory on GitHub. Reviewed sources take precedence over it.