Horizon Alert
Summary of the vulnerability and why it matters
A vulnerability exists in versions of React Router and Remix.js related to session storage, where an attacker could potentially cause the session to interact with unintended file locations. This could lead to the server accessing or modifying files outside the designated session directory, depending on server process permissions and application logic.
- Session storage code could be misused.
- Matters if session data is handled improperly.
- Confirm if our applications use this code.
Attack Path
How an attacker could exploit the issue
An attacker could leverage this vulnerability by sending specially crafted requests to a web application that uses vulnerable versions of React Router or Remix with `createFileSessionStorage` and unsigned cookies. This could lead to the application attempting to read or write session data from unintended file locations on the server, potentially exposing sensitive information if the attacker can control the target file path and if the file matches the expected session format.
- Attacker sends crafted requests to the web application.
- Vulnerable session storage function handles unsigned cookies.
- Risk of unauthorized file access and session data manipulation.
Live Threat
Current exploitation, exposure, and threat context
When used with unsigned cookies and the `createFileSessionStorage()` function, an attacker could manipulate the session storage to read or write from unintended file locations. This could impact server-side session data, and the attacker might see session data if the application logic returns it. The success of such an attack depends on the web server process's file system permissions.
- Server-side session data.
- Unintended file access with session data.
- Potential exposure of session contents.
Operational Fix
Recommended remediation, mitigation, and detection steps
Application owners and infrastructure teams are likely responsible for addressing this vulnerability in React Router and Remix Node.js deployments. The first practical step is to identify all instances of the affected technologies, confirm their exposure and criticality, and then determine the accountable owner for remediation.
- Application owners should investigate usage.
- Verify reachability and business criticality.
- Plan remediation based on risk.
