Vulnerability library
Security checkAugust 07, 2026

SvelteKit: ReDoS (O(n^2)) in content negotiation — unauthenticated DoS via the Accept header

Understand the exposure, see the recommended fix, and check whether your own website has related weaknesses.

Medium severitynpm@sveltejs/kit

Check your website

Find this and other vulnerabilities with a free scan.

Your scan runs on your computer. No account required.

Description

SvelteKit is vulnerable to remote CPU-exhaustion DoS attacks via specifically-crafted Accept headers. The impact is mitigated by default header length limits on most platforms, but in the case of raised or absent limits a denial of service is possible.

Recommendation

Update the @sveltejs/kit package to the latest compatible version. Followings are version details:

  • Affected version(s): <= 2.70.1
  • Patched version(s): 2.70.2

References

Could your website be exposed too?

SmartScanner can check your website for SvelteKit: ReDoS (O(n^2)) in content negotiation — unauthenticated DoS via the Accept header and gives you actionable findings to investigate.

Start a free scan

Related Issues

See something that needs correcting? Let us knowUpdated August 07, 2026