Open Redirect Vulnerability in ruby-sinatra: Exploiting X-Forwarded-Host Header
Summary
DEBIAN-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. Affects ruby-sinatra versions < 4.1.1-2. Fixed in 4.1.1-2. How to fix ↓
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Background
ruby-sinatra is a lightweight web application framework for Ruby, designed for simplicity and flexibility in building web applications. It allows developers to create web applications quickly with minimal effort. However, certain versions of ruby-sinatra are vulnerable to an open redirect attack due to improper handling of the X-Forwarded-Host (XFH) header, which can lead to serious security issues.
Vulnerability Detail
The vulnerability arises from the reliance on untrusted inputs in security decisions, specifically through the X-Forwarded-Host header. When a request is made to a method with a redirect applied, an attacker can manipulate this header to redirect users to arbitrary addresses. This can lead to open redirect attacks, which can be exploited for cache poisoning or routing-based Server-Side Request Forgery (SSRF) if the application is behind a reverse proxy like Nginx.
How To Fix
Minimum fixed version
4.1.1-2
This is the first release that contains the fix.
sudo apt-get install --only-upgrade ruby-sinatraTip — Not sure which version your app runs? Vulert can match this fix to it. Scan free →
Workaround
As a temporary workaround, you can implement validation on the X-Forwarded-Host header to ensure it only contains trusted domains. This can be done by adding a middleware in your Sinatra application that checks the header before processing requests.
Conclusion
The ruby-sinatra package has a critical vulnerability related to the handling of the X-Forwarded-Host header, which can lead to open redirect attacks. It is essential to update to the patched version 4.1.1-2 or later to mitigate this risk. Additionally, implementing validation on the header can serve as a temporary workaround.
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FAQ
The X-Forwarded-Host header is used to identify the original host requested by the client in the case of a proxy or load balancer.
If exploited, this vulnerability can lead to open redirect attacks, allowing attackers to redirect users to malicious sites or perform cache poisoning.
If you are using ruby-sinatra versions prior to 4.1.1-2, your application is vulnerable. You can check for vulnerabilities using Vulert without any signup.
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References
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