CVE-2015-7576 in Ruby on Rails
Summary
by MITRE
The http_basic_authenticate_with method in actionpack/lib/action_controller/metal/http_authentication.rb in the Basic Authentication implementation in Action Controller in Ruby on Rails before 3.2.22.1, 4.0.x and 4.1.x before 4.1.14.1, 4.2.x before 4.2.5.1, and 5.x before 5.0.0.beta1.1 does not use a constant-time algorithm for verifying credentials, which makes it easier for remote attackers to bypass authentication by measuring timing differences.
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Analysis
by VulDB Data Team • 07/06/2022
The vulnerability identified as CVE-2015-7576 represents a critical timing side-channel attack against Ruby on Rails applications implementing basic authentication. This flaw exists within the http_basic_authenticate_with method located in actionpack/lib/action_controller/metal/http_authentication.rb, which is part of the Action Controller framework's authentication mechanism. The vulnerability stems from the implementation's failure to employ constant-time algorithms when comparing authentication credentials, creating a predictable timing pattern that can be exploited by malicious actors.
The technical nature of this vulnerability falls under CWE-208, which specifically addresses timing side-channel attacks where attackers can measure the time taken to perform cryptographic operations to infer information about the credentials being verified. In this case, the Basic Authentication implementation does not use constant-time string comparison functions, allowing attackers to perform timing analysis against authentication requests. When a user attempts to authenticate, the system's response time varies depending on how many characters of the password match the stored value, enabling an attacker to gradually determine the correct credentials through repeated timing measurements.
The operational impact of this vulnerability is significant for organizations running affected versions of Ruby on Rails, as it provides a sophisticated attack vector that can bypass authentication mechanisms without requiring brute force computation or network sniffing. Attackers can exploit this weakness to gain unauthorized access to protected resources by carefully measuring response times from authentication endpoints. The vulnerability affects multiple major version lines of Rails including 3.2.x, 4.0.x, 4.1.x, 4.2.x, and early 5.x releases, making it widespread across many production environments that may not have been properly updated.
The attack pattern typically involves sending multiple authentication requests with varying credentials and measuring the response times to determine which characters of a password are correct. This technique, known as timing-based credential guessing, can be automated and becomes increasingly effective with each additional request. The vulnerability directly maps to ATT&CK technique T1110.001, which describes credential guessing using timing attacks, and T1110.002, which covers password guessing with timing analysis. Organizations using affected Rails versions are particularly vulnerable because the flaw exists at the framework level, meaning that any application relying on the basic authentication mechanism is susceptible to this attack vector.
Mitigation strategies for CVE-2015-7576 require immediate patching of affected Ruby on Rails installations to versions that implement constant-time credential verification. Organizations should prioritize updating their applications to Rails 3.2.22.1, 4.1.14.1, 4.2.5.1, or 5.0.0.beta1.1 respectively, depending on their current version. Additionally, implementing additional security measures such as rate limiting, account lockout mechanisms, and monitoring for unusual authentication patterns can provide defense in depth. Network-level protections including intrusion detection systems that monitor for timing-based attack patterns and application firewalls that can detect and block suspicious authentication attempts should also be considered as supplementary controls to protect against exploitation of this vulnerability.