CVE-2026-66062— SvelteKit: ReDoS (O(n^2)) in content negotiation — unauthenticated DoS via the Accept header
Quick assessment
Affected
sveltejs kit
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.
SvelteKit是Svelte公司开源的一个使用Svelte框架快速开发健壮、高性能 Web 应用程序的工具。 SvelteKit 2.70.2之前版本存在资源管理错误漏洞，该漏洞源于内容协商标头解析器使用容易受到二次回溯的正则表达式，恶意构造的标头值可能导致过度CPU消耗，降低或拒绝服务。
Possible ATT&CK Techniques 1 AI
T1496 · Resource Hijacking
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I. Basic Information for CVE-2026-66062
Vulnerability Information
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Vulnerability Title
SvelteKit: ReDoS (O(n^2)) in content negotiation — unauthenticated DoS via the Accept header
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Source: CVE Program / CVE List V5
Vulnerability Type
CWE-1333
Source: CVE Program / CVE List V5
Vulnerability Title
SvelteKit 资源管理错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
SvelteKit是Svelte公司开源的一个使用Svelte框架快速开发健壮、高性能 Web 应用程序的工具。 SvelteKit 2.70.2之前版本存在资源管理错误漏洞，该漏洞源于内容协商标头解析器使用容易受到二次回溯的正则表达式，恶意构造的标头值可能导致过度CPU消耗，降低或拒绝服务。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)
Affected Products
II. Public POCs for CVE-2026-66062
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Patches & Fixes for CVE-2026-66062 (1)
Vendor Advisories for CVE-2026-66062 (1)
Vendor Pages for CVE-2026-66062 (1)
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🔗 Release @sveltejs/kit@2.70.2 · sveltejs/kit · GitHub x_refsource_MISC
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SvelteKit 2.49.0 before 2.53.3 Denial of Service via form
Same weakness: CWE-1333
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