CVE-2025-27221 refers to a vulnerability in the URI gem for Ruby programming language, specifically before the release of version 1..3. In this post, we will dive deep into the nature of the issue, provide code snippets demonstrating the vulnerability, and share links to original references. Finally, we will discuss the exploit details and how you can fix this vulnerability in your Ruby applications.
Nature of the Vulnerability
The URI gem is extensively used in Ruby for uniformly identifying resources across the internet and handling URIs (Uniform Resource Identifiers). When using specific URI handling methods, such as URI.join, URI#merge, and URI#+, the URI gem inadvertently retains the authentication credentials from the userinfo segment of the URI even after changing the host.
As a result, sensitive information like usernames and passwords can leak, allowing an attacker to gain unauthorized access to users' accounts.
Code Snippet Demonstrating the Vulnerability
Here is a code snippet that shows how the userinfo is leaked when using the URI.join method with different URIs:
require 'uri'
# Original URI with userinfo
uri_1 = URI.parse('http://username:password@example.com';)
# New URI without userinfo - This URI should replace the original URI
uri_2 = URI.parse('http://www.example.org';)
# Using URI.join to combine the URIs
new_uri = URI.join(uri_1, uri_2)
# Resulting URI should have removed the userinfo
puts "Expected new_uri: http://www.example.org";
puts "Actual new_uri: #{new_uri}"
In this example, it is expected that uri_1 is replaced with uri_2 and the resulting URI (new_uri) should have had the userinfo segment removed. However, due to the vulnerability in the URI gem, the userinfo segment remains:
Expected new_uri: http://www.example.org
Actual new_uri: http://username:password@example.org
Here are some of the official references associated with this vulnerability
1. CVE Reference
2. Ruby-lang Security Announcement
3. GitHub Commit Fixing the Issue
Exploit Details
An attacker could use this vulnerability by intercepting the leaked userinfo from the application's network traffic or by analyzing the application's log files that might contain sensitive URI data. Once the attacker has access to the leaked credentials, they can exploit it to perform unauthorized actions on the compromised accounts.
Mitigation Steps
To fix this vulnerability in your Ruby applications, you should update the URI gem to version 1..3 or later. Make sure to follow these steps:
Verify your current URI gem version
gem list '^uri$'
If the version is earlier than 1..3, proceed to the next step.
Update the URI gem
gem update uri
Verify that the update was successful
gem list '^uri$'
Conclusion
CVE-2025-27221 identifies a significant vulnerability in the URI gem for Ruby that could lead to the inadvertent leakage of authentication credentials. Keeping your systems and applications updated is essential to ensure the security of your users' data. Make sure to always update your gems and dependencies to fix any vulnerabilities that might be discovered and patched.
Timeline
Published on: 03/04/2025 00:15:31 UTC
Last modified on: 03/05/2025 14:58:05 UTC