CVE-2026-66062: CWE-1333: Inefficient Regular Expression Complexity in sveltejs kit
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.
AI Analysis
Technical Summary
CVE-2026-66062 describes a vulnerability in SvelteKit's request handling prior to version 2.70.2. The content negotiation header parser uses a regular expression that is vulnerable to inefficient complexity, specifically quadratic backtracking. An attacker can exploit this by sending a specially crafted header value (e.g., Accept header) that triggers excessive CPU usage, leading to performance degradation or denial of service. The vulnerability is classified under CWE-1333 (Inefficient Regular Expression Complexity). The issue is resolved in SvelteKit version 2.70.2.
Potential Impact
The vulnerability allows an unauthenticated remote attacker to cause excessive CPU consumption on the affected server by sending maliciously crafted HTTP headers. This can degrade the performance of the web application or cause denial of service. There is no impact on confidentiality or integrity, only availability is affected.
Mitigation Recommendations
Upgrade SvelteKit to version 2.70.2 or later, where the inefficient regular expression has been fixed. No other mitigation is indicated. Patch status is confirmed by the version fix information. There is no vendor advisory content contradicting this.
CVE-2026-66062: CWE-1333: Inefficient Regular Expression Complexity in sveltejs kit
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.
CVSS v3.1
Score 5.3medium
Affected software
sveltejs
kit
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Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
CVE-2026-66062 describes a vulnerability in SvelteKit's request handling prior to version 2.70.2. The content negotiation header parser uses a regular expression that is vulnerable to inefficient complexity, specifically quadratic backtracking. An attacker can exploit this by sending a specially crafted header value (e.g., Accept header) that triggers excessive CPU usage, leading to performance degradation or denial of service. The vulnerability is classified under CWE-1333 (Inefficient Regular Expression Complexity). The issue is resolved in SvelteKit version 2.70.2.
Potential Impact
The vulnerability allows an unauthenticated remote attacker to cause excessive CPU consumption on the affected server by sending maliciously crafted HTTP headers. This can degrade the performance of the web application or cause denial of service. There is no impact on confidentiality or integrity, only availability is affected.
Mitigation Recommendations
Upgrade SvelteKit to version 2.70.2 or later, where the inefficient regular expression has been fixed. No other mitigation is indicated. Patch status is confirmed by the version fix information. There is no vendor advisory content contradicting this.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- GitHub_M
- Date Reserved
- 2026-07-23T23:25:28.896Z
- Cvss Version
- 3.1
- State
- PUBLISHED
Threat ID: 6a7611e1bf8831d539ac7f4a
Added to database: 08/07/2026, 17:12:01 UTC
Last enriched: 08/07/2026, 17:31:57 UTC
Last updated: 09/21/2026, 22:01:36 UTC
Views: 60
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