CVE-2026-128123: SvelteKit: `@sveltejs/adapter-node` crashes when proxying certain requests via `fetch`
In affected versions, @sveltejs/adapter-node can attempt to add a header to an immutable request in a context that causes the server to crash, denying service to any other requests routed to that server.
References
- github.com/advisories/GHSA-rqw3-x7hx-mm3p
- github.com/sveltejs/kit/commit/04756a1f7a4f73e34f1934895340a46de84fc164
- github.com/sveltejs/kit/commit/0a2e58cbccdd46cac20aa5af4e2edf17e0da11dd
- github.com/sveltejs/kit/pull/17620
- github.com/sveltejs/kit/releases/tag/@sveltejs/adapter-node@5.5.8
- github.com/sveltejs/kit/releases/tag/@sveltejs/adapter-node@6.0.1
- github.com/sveltejs/kit/security/advisories/GHSA-rqw3-x7hx-mm3p
- nvd.nist.gov/vuln/detail/CVE-2026-128123
Code Behaviors & Features
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