CVE-2009-3086 in Ruby on Rails
Summary
by MITRE
A certain algorithm in Ruby on Rails 2.1.0 through 2.2.2, and 2.3.x before 2.3.4, leaks information about the complexity of message-digest signature verification in the cookie store, which might allow remote attackers to forge a digest via multiple attempts.
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Analysis
by VulDB Data Team • 08/22/2021
This vulnerability resides in the cookie store implementation of Ruby on Rails framework versions between 2.1.0 and 2.2.2, as well as 2.3.x versions prior to 2.3.4. The flaw manifests in how the framework handles message-digest signature verification for cookie data, creating a timing side-channel attack vector that exposes information about the cryptographic complexity during verification processes. The vulnerability is classified under CWE-347 as it involves improper verification of cryptographic signatures, specifically through timing analysis that reveals information about the verification algorithm's behavior. Attackers can exploit this weakness by making multiple signature verification attempts and measuring response times to deduce information about the cryptographic operations, ultimately enabling them to forge valid signatures for cookie data.
The technical implementation flaw occurs in the cookie store's digest verification routine where the framework does not employ constant-time comparison algorithms when validating message-digest signatures. This timing variation allows attackers to perform statistical analysis on verification response times, inferring information about the expected digest values. The vulnerability specifically targets the cryptographic verification process where the system compares computed hashes with stored signatures, and the non-constant time execution introduces measurable differences that can be exploited. According to ATT&CK framework category T1211, this represents a timing attack technique that leverages implementation details to extract sensitive information. The flaw affects the integrity protection mechanism of the cookie store, undermining the security guarantees that should prevent unauthorized modifications to session data.
The operational impact of this vulnerability is significant for applications relying on Rails cookie-based session management, as it enables remote attackers to bypass authentication mechanisms and potentially gain unauthorized access to user sessions. Attackers can systematically forge valid signatures by exploiting the timing information leak, allowing them to create malicious cookies that will be accepted by the application's verification process. This could lead to session hijacking, privilege escalation, and unauthorized access to protected application resources. The vulnerability affects the confidentiality and integrity of session data, as the cookie store's security model relies on the assumption that signature verification is immune to timing-based attacks. Applications using affected Rails versions may be vulnerable to attacks that compromise user sessions without requiring direct access to cryptographic keys or other sensitive information.
Mitigation strategies for this vulnerability require immediate patching of affected Rails versions to 2.3.4 or later, where the framework implements constant-time signature verification algorithms. Organizations should also consider implementing additional security measures such as using stronger cryptographic algorithms, implementing rate limiting on signature verification attempts, and monitoring for unusual patterns in request timing. The fix addresses the root cause by ensuring that signature verification operations take constant time regardless of input values, eliminating the timing side-channel that enabled the attack. Security teams should conduct comprehensive testing to verify that all affected applications have been properly updated and that the new constant-time comparison implementations are functioning correctly. This vulnerability highlights the importance of implementing cryptographic operations with constant-time complexity to prevent information leakage through timing analysis, a principle that aligns with security best practices outlined in NIST SP 800-57 and other cryptographic standards.