CVE-2025-61686
Published: 10 January 2026
Summary
CVE-2025-61686 is a critical-severity Path Traversal (CWE-22) vulnerability in Shopify React-Router\/Node. Its CVSS base score is 9.1 (Critical).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked in the top 3.7% of CVEs by exploit likelihood; it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified are NIST 800-53 AC-6 (Least Privilege) and SI-10 (Information Input Validation).
Deeper analysis
CVE-2025-61686 is a path traversal vulnerability (CWE-22) affecting React Router and related packages. It impacts @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. The issue arises when createFileSessionStorage() is used with an unsigned cookie, allowing session operations to target locations outside the specified session file directory. The CVSS v3.1 base score is 9.1 (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H), highlighting high integrity and availability impacts with no direct confidentiality loss.
An unauthenticated network attacker can exploit this by crafting a malicious unsigned cookie to trigger session read or write operations on arbitrary files outside the intended directory. Exploitation success depends on the web server process's file system permissions. While read files cannot be directly returned to the attacker, a successful read occurs only if the file matches the expected session file format, populating the data into the server-side session. This session data is not directly exposed unless application logic returns specific session information. Write operations could similarly overwrite files outside the directory if permissions allow.
The GitHub security advisory at https://github.com/remix-run/react-router/security/advisories/GHSA-9583-h5hc-x8cw details the patch, which addresses the issue in @react-router/node version 7.9.4, @remix-run/deno version 2.17.2, and @remix-run/node version 2.17.2. Security practitioners should upgrade to these versions and review applications using file-based session storage with unsigned cookies for exposure.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-1468
Vulnerability details
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,…
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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.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
Path traversal in public-facing web session storage directly enables remote exploitation (T1190) with arbitrary local file reads (T1005) and overwrites (T1565.001).
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
SI-2 requires timely identification, reporting, and correction of software flaws, directly addressing this path traversal vulnerability through patching to the fixed versions.
SI-10 enforces validation of information inputs like the unsigned cookie used to derive session file paths, preventing path traversal outside the intended directory.
AC-6 applies least privilege to the web server process, restricting file system access to only the session directory and blocking exploitation even if traversal is attempted.