Answer in brief
CVE-2026-66062 records a Medium severity (CVSS 5.3) vulnerability in SvelteKit: ReDoS (O(n^2)) in content negotiation — unauthenticated DoS via the Accept header. The current sources do not mark it as known exploited. The current feed maps sveltejs/kit (generic), @sveltejs/kit (npm). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
CVSS is 5.3. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps sveltejs/kit (generic), @sveltejs/kit (npm). Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| sveltejs/kitgeneric | <2.70.2 | 2.70.2 |
| @sveltejs/kitnpm | <=2.70.1 | 2.70.2 |
Published upstream
Aug 7, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Oct 24, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Aug 7, 2026
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.
Quoted source text, attributed separately from HOL analysis.