React Router has Path Traversal in File Session Storage

Summary

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.

Timeline

1. Jan 10, 2026, 2:41 AM UTCCVE published
2. Jan 12, 2026, 1:58 PM UTCCISA SSVC assessment

   Exploitation: none · Automatable: yes · Technical impact: partial

3. Jul 15, 2026, 1:25 AM UTCRecord last updated
4. Oct 28, 2026EPSS reached 10%

   FIRST estimates at least a 10% chance of exploitation in the next 30 days

Affected versions

• remix-run react-router

  @remix-run/deno < 2.17.2, @remix-run/node < 2.17.2

• @react-router/nodenpm

  From 7.0.0 · fixed in 7.9.4

• @remix-run/nodenpm

  fixed in 2.17.2

• @remix-run/denonpm

  fixed in 2.17.2

References 4