CVE-2024-21510

Versions of the package sinatra from 0.0.0 are vulnerable to Reliance on Untrusted Inputs in a Security Decision via the X-Forwarded-Host (XFH) header. When making a request to a method with redirect applied, it is possible to trigger an Open Redirect Attack by inserting an arbitrary address into this header. If used for caching purposes, such as with servers like Nginx, or as a reverse proxy, without handling the X-Forwarded-Host header, attackers can potentially exploit Cache Poisoning or Routing-based SSRF.

Weakness

The product uses a protection mechanism that relies on the existence or values of an input, but the input can be modified by an untrusted actor in a way that bypasses the protection mechanism.

Affected Software

Extended Description

Developers may assume that inputs such as cookies, environment variables, and hidden form fields cannot be modified. However, an attacker could change these inputs using customized clients or other attacks. This change might not be detected. When security decisions such as authentication and authorization are made based on the values of these inputs, attackers can bypass the security of the software. Without sufficient encryption, integrity checking, or other mechanism, any input that originates from an outsider cannot be trusted.

Potential Mitigations

• Store state information and sensitive data on the server side only.
• Ensure that the system definitively and unambiguously keeps track of its own state and user state and has rules defined for legitimate state transitions. Do not allow any application user to affect state directly in any way other than through legitimate actions leading to state transitions.
• If information must be stored on the client, do not do so without encryption and integrity checking, or otherwise having a mechanism on the server side to catch tampering. Use a message authentication code (MAC) algorithm, such as Hash Message Authentication Code (HMAC) [REF-529]. Apply this against the state or sensitive data that has to be exposed, which can guarantee the integrity of the data - i.e., that the data has not been modified. Ensure that a strong hash function is used (CWE-328).
• Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
• With a stateless protocol such as HTTP, use a framework that maintains the state for you.
• Examples include ASP.NET View State [REF-756] and the OWASP ESAPI Session Management feature [REF-45].
• Be careful of language features that provide state support, since these might be provided as a convenience to the programmer and may not be considering security.
• Understand all the potential areas where untrusted inputs can enter your software: parameters or arguments, cookies, anything read from the network, environment variables, reverse DNS lookups, query results, request headers, URL components, e-mail, files, filenames, databases, and any external systems that provide data to the application. Remember that such inputs may be obtained indirectly through API calls.
• Identify all inputs that are used for security decisions and determine if you can modify the design so that you do not have to rely on submitted inputs at all. For example, you may be able to keep critical information about the user’s session on the server side instead of recording it within external data.

References

• https://github.com/sinatra/sinatra/blob/b626e2d82c23b4fde0b51782fd32ca27ccde1d1a/lib/sinatra/base.rb%23L319
• https://github.com/sinatra/sinatra/blob/b626e2d82c23b4fde0b51782fd32ca27ccde1d1a/lib/sinatra/base.rb%23L323C1-L343C17
• https://github.com/sinatra/sinatra/pull/2010
• https://security.snyk.io/vuln/SNYK-RUBY-SINATRA-6483832