SvelteKit: ReDoS (O(n^2)) in content negotiation — unauthenticated DoS via the Accept header
Priority LOW 31CWE-1333Published · Updated
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Impact type
- Denial of service
- Confidentiality · integrity · availability
- None · None · Low
- Fix status
- Fixed
Attack profile from CVSS 3.1 · CNA. Fix status from CNA and GitHub. Impact type from CWE-1333.
Summary
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.
Why it matters now
Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00507 43rd percentileScored 2026-11-07
Fix Fixed kit (sveltejs): 2.70.2@sveltejs/kit (npm): 2.70.2
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- Yes
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| sveltejs | kit | before 2.70.2 | 2.70.2 | Patch available | CNA |
| — | @sveltejs/kit (npm) | before 2.70.2 | 2.70.2 | Patch available | GHSA-29g2-3rmr-qm68 |
- kit Vendorsveltejs Affected before 2.70.2 Fixed in 2.70.2 Patch available CNA
- @sveltejs/kit (npm) Vendor— Affected before 2.70.2 Fixed in 2.70.2 Patch available GHSA-29g2-3rmr-qm68
Remediation
- Fix · CNA kit (sveltejs) Fixed in 2.70.2
- Fix · GHSA-29g2-3rmr-qm68 @sveltejs/kit (npm) Fixed in 2.70.2 Advisory →
Timeline
- 2026-10-02 Threatist record created from CVE-2026-66062
- 2026-10-03 Alias added: GHSA-29g2-3rmr-qm68
References
More sveltejs vulnerabilities
- TI-2023-13469 SvelteKit framework has Insufficient CSRF protection for CORS requests CVSS 3.1HIGH 8.8
- TI-2023-13464 SvelteKit has Insufficient Cross-Site Request Forgery Protection CVSS 3.1HIGH 8.8
- TI-2024-15660 Sending a GET or HEAD request with a body crashes SvelteKit CVSS 3.1HIGH 7.5
- TI-2024-30159 Potential mXSS vulnerability due to improper HTML escaping in svelte CVSS 3.1MEDIUM 6.1
- TI-2025-23466 SvelteKit allows XSS via tracked search_params CVSS 3.1MEDIUM 5.4
- TI-2025-13940 Svelte 5.46.0 - Hydratable Key Script-Breakout XSS (SSR) CVSS 4.0MEDIUM 5.3
Sources
- CVE-2026-66062 · CVE Program
- CVE-2026-66062 · NVD
- FIRST EPSS
- GHSA-29g2-3rmr-qm68 · GitHub Advisory Database · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences