CVE-2025-61686
CriticalCVSS 9.1Exploitation Probability (EPSS)
Very high risk97th percentile - higher than 97% of all known CVEs
Summary
In React Router (versions 7.0.0–7.9.3), Remix Deno (before 2.17.2), and Remix Node (before 2.17.2), a vulnerability allows reading/writing session files outside the intended directory when using unsigned cookies with createFileSessionStorage().
Risk Assessment
An attacker may access session files outside the designated directory, potentially leading to session data leakage or modification. Success depends on web server permissions, and read data is not directly returned unless application logic exposes it.
Recommendation
Immediately update @react-router/node to version 7.9.4, @remix-run/deno to version 2.17.2, and @remix-run/node to version 2.17.2. As a workaround, use signed cookies for sessions.
Original NVD description (English source)
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.