CVE-2026-34077: React Router vulnerable to Denial of Service via reflected user input in single-fetch
A DoS vulnerability exists in the React Router v7 Framework Mode, as well as Remix v2.9.0+ with Single Fetch enabled. In some scenarios the underlying serialization algorithm can become a bottleneck when encoding specific types of data into server responses. Please upgrade to React Router v7.14.0 or later.
[!NOTE] This does not impact your React Router application if you are using Declarative Mode (
<BrowserRouter>) or Data Mode (createBrowserRouter/<RouterProvider>).
References
- github.com/advisories/GHSA-rxv8-25v2-qmq8
- github.com/jacob-ebey/turbo-stream/blob/v2.4.1/src/flatten.ts
- github.com/jacob-ebey/turbo-stream/blob/v2.4.1/src/unflatten.ts
- github.com/remix-run/react-router/commit/59811921d3c7d599077b8cadccdcd65a233165e0
- github.com/remix-run/react-router/security/advisories/GHSA-rxv8-25v2-qmq8
- nvd.nist.gov/vuln/detail/CVE-2026-34077
Code Behaviors & Features
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