CVE-2026-66062: CWE-1333: Inefficient Regular Expression Complexity in sveltejs kit
SvelteKit versions prior to 2.70.2 contain a vulnerability in the content negotiation header parser where a regular expression used for parsing headers like Accept is susceptible to quadratic backtracking. This can allow a maliciously crafted header to cause excessive CPU consumption, potentially degrading service or causing denial of service. The issue is fixed in version 2.70.2.
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 versions prior to 2.70.2 contain a vulnerability in the content negotiation header parser where a regular expression used for parsing headers like Accept is susceptible to quadratic backtracking. This can allow a maliciously crafted header to cause excessive CPU consumption, potentially degrading service or causing denial of service. The issue is fixed in version 2.70.2.
CVSS v3.1
Score 5.3medium
Affected software
Run on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
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
- Remediation Level
- null
Threat ID: 6a7611e1bf8831d539ac7f4a
Added to database: 08/07/2026, 17:12:01 UTC
Last enriched: 08/07/2026, 17:31:57 UTC
Last updated: 08/07/2026, 17:40:26 UTC
Views: 4
Community Reviews
0 reviewsCrowdsource mitigation strategies, share intel context, and vote on the most helpful responses. Sign in to add your voice and help keep defenders ahead.
Want to contribute mitigation steps or threat intel context? Sign in or create an account to join the community discussion.
Actions
Updates to AI analysis require Pro Console access. Upgrade inside Console → Billing.
Need more coverage?
Upgrade to Pro Console for AI refresh and higher limits.
For incident response and remediation, OffSeq services can help resolve threats faster.
Latest Threats
Check if your credentials are on the dark web
Instant breach scanning across billions of leaked records. Free tier available.