In short
- CVE-2026-66062 is a MEDIUM (CVSS 5.3) vulnerability affecting @sveltejs/kit.
- Chance of exploitation in the next 30 days (EPSS): 0.51%, higher than 43.3% of all vulnerabilities.
- Fix: update to 2.70.2 or later.
| Package | Affected versions | Patched versions |
|---|
| @sveltejs/kit npm | < 2.70.2
| 2.70.2
|
Description
Impact
SvelteKit is vulnerable to remote CPU-exhaustion DoS attacks via specifically-crafted Accept headers. The impact is mitigated by default header length limits on most platforms, but in the case of raised or absent limits a denial of service is possible.
Patches
The vulnerability is patched in @sveltejs/kit version 2.70.2.
NVD description
SvelteKit is a framework for rapidly developing robust, performant web applications using Svelte. Prior to 2.70.2, the content negotiation header parser used by SvelteKit's request handling (for headers such as Accept) uses a regular expression vulnerable to quadratic backtracking, so a maliciously crafted header value can cause excessive CPU consumption and degrade or deny service. Version 2.70.2 fixes the issue.
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