CVE-2012-3424 in Ruby on Rails
Summary
by MITRE
The decode_credentials method in actionpack/lib/action_controller/metal/http_authentication.rb in Ruby on Rails 3.x before 3.0.16, 3.1.x before 3.1.7, and 3.2.x before 3.2.7 converts Digest Authentication strings to symbols, which allows remote attackers to cause a denial of service by leveraging access to an application that uses a with_http_digest helper method, as demonstrated by the authenticate_or_request_with_http_digest method.
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Analysis
by VulDB Data Team • 03/27/2021
The vulnerability described in CVE-2012-3424 represents a critical denial of service weakness in the Ruby on Rails framework that specifically targets the HTTP digest authentication implementation. This flaw exists within the decode_credentials method located in actionpack/lib/action_controller/metal/http_authentication.rb, where the framework processes authentication strings by converting them to symbols. The vulnerability affects multiple versions of Rails including 3.x before 3.0.16, 3.1.x before 3.1.7, and 3.2.x before 3.2.7, making it a widespread issue across the framework's major release lines during that period.
The technical mechanism behind this vulnerability involves the improper handling of authentication credentials during the digest authentication process. When an application utilizing Rails employs the with_http_digest helper method, particularly through the authenticate_or_request_with_http_digest method, the framework's decode_credentials function processes incoming authentication strings by converting them to Ruby symbols. This symbol conversion creates a path for attackers to exploit by crafting specially malformed authentication strings that cause the application to consume excessive memory resources. The conversion process becomes problematic because Ruby symbols are not garbage collected in the same manner as regular strings, leading to potential memory exhaustion when attackers repeatedly submit malicious credential data.
The operational impact of this vulnerability extends beyond simple denial of service conditions, as it can effectively render applications unavailable to legitimate users while consuming system resources. Attackers can leverage this weakness by sending crafted HTTP requests containing specially formatted digest authentication headers, which triggers the vulnerable code path and causes the application server to allocate increasing amounts of memory. This behavior aligns with attack patterns classified under the MITRE ATT&CK framework's privilege escalation and denial of service tactics, specifically targeting application-level vulnerabilities that can be exploited without authentication. The vulnerability is particularly dangerous because it requires no prior authentication to exploit and can be executed against any Rails application that implements digest authentication.
Security professionals should recognize this issue as a classic example of resource exhaustion through improper input handling, which maps to CWE-400 - Uncontrolled Resource Consumption. The flaw demonstrates how seemingly innocuous operations like credential conversion can become attack vectors when proper input validation and resource management are not implemented. Organizations using affected Rails versions should immediately apply the security patches released by the Ruby on Rails team, which address the symbol conversion issue in the decode_credentials method. Additionally, implementing proper request rate limiting and monitoring for unusual authentication patterns can help detect and mitigate exploitation attempts. The vulnerability also highlights the importance of thorough code review processes for authentication mechanisms and the need for proper handling of user-supplied data in web application frameworks.