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CVE-2026-82261 – Denial of Service (CPU Exhaustion) – SvelteKit (@sveltejs/kit) 2.49.0 to 2.52.1

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Summary

CVE-2026-82261 is a CPU exhaustion / denial-of-service vulnerability (CWE-400: Uncontrolled Resource Consumption) affecting @sveltejs/kit. It impacts deployments that have enabled the experimental remote functions feature and use the form remote function, where malformed form data submitted by an attacker triggers excessive CPU consumption during deserialization, rendering the server unresponsive. The issue carries a high severity rating and is remotely exploitable without authentication.

Technical details

  • Root cause: SvelteKit’s remote form deserialization logic does not adequately bound the cost of processing malformed or crafted form submissions before expensive deserialization work is performed.
  • Trigger condition: The affected application must have experimental.remoteFunctions enabled and use the form remote function.
  • Attack vector: Network — an unauthenticated attacker sends specially crafted/malformed form data to an exposed SvelteKit endpoint.
  • Impact: Excessive server-side CPU consumption leading to denial of service; no confidentiality or integrity impact.

Affected software

  • @sveltejs/kit versions 2.49.0 through 2.52.1 (inclusive), when experimental remote functions and the form function are enabled.

Severity

  • CVSS v4.0: 8.7 (HIGH) — CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
  • CVSS v3.1: 7.5 (HIGH) — CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Mitigation and recommended actions

  • Immediate: Upgrade @sveltejs/kit to version 2.52.2 or later, which contains the fix.
  • If immediate patching is not possible: Disable the experimental remote functions feature (experimental.remoteFunctions), or ensure any form remote function handlers validate incoming form data (e.g., field counts/sizes) before performing expensive processing.

How IONIX identifies potentially affected assets

IONIX matches the following signal against data already collected when it crawled the asset; identifying the technology sends no request beyond that crawl.

  • Raw HTTP response body: /_app/immutable/entry/start.

References

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