CVE-2026-34077
HIGH7.5React Router vulnerable to Denial of Service via reflected user input in single-fetch
Description
A DoS vulnerability exists in the React Router v7 [Framework Mode](https://reactrouter.com/start/modes#framework), as well as Remix v2.9.0+ with [Single Fetch](https://v2.remix.run/docs/guides/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](https://reactrouter.com/start/modes#declarative) (`<BrowserRouter>`) or [Data Mode](https://reactrouter.com/start/modes#data) (`createBrowserRouter`/`<RouterProvider>`).
Affected packages (2)
- npm/react-router>= 7.0.0, < 7.14.0
- npm/turbo-streamfrom 0, < 3.0.0
CVSS scores
| Source | Version | Severity | Vector |
|---|---|---|---|
| osv | CVSS 3.1 | HIGH7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
References (6)
- ADVISORYhttps://nvd.nist.gov/vuln/detail/CVE-2026-34077
- PATCHhttps://github.com/remix-run/react-router
- WEBhttps://github.com/jacob-ebey/turbo-stream/blob/v2.4.1/src/flatten.ts#L175-L177
- WEBhttps://github.com/jacob-ebey/turbo-stream/blob/v2.4.1/src/unflatten.ts#L185-L189
- WEBhttps://github.com/remix-run/react-router/commit/59811921d3c7d599077b8cadccdcd65a233165e0
- WEBhttps://github.com/remix-run/react-router/security/advisories/GHSA-rxv8-25v2-qmq8