CVE-2013-0263 in Rack
Summary
by MITRE
Rack::Session::Cookie in Rack 1.5.x before 1.5.2, 1.4.x before 1.4.5, 1.3.x before 1.3.10, 1.2.x before 1.2.8, and 1.1.x before 1.1.6 allows remote attackers to guess the session cookie, gain privileges, and execute arbitrary code via a timing attack involving an HMAC comparison function that does not run in constant time.
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Analysis
by VulDB Data Team • 12/29/2021
The vulnerability described in CVE-2013-0263 represents a critical security flaw in the Rack web application framework's session management system. This issue affects multiple versions of Rack including 1.5.x before 1.5.2, 1.4.x before 1.4.5, 1.3.x before 1.3.10, 1.2.x before 1.2.8, and 1.1.x before 1.1.6, making it a widespread concern across various web applications built on this framework. The vulnerability stems from an insecure implementation of HMAC comparison operations that fail to execute in constant time, creating a timing attack surface that can be exploited by remote attackers to compromise session integrity.
The technical flaw manifests in the HMAC comparison function used to validate session cookies within Rack's session management system. When comparing HMAC values for session validation, the implementation does not perform constant-time comparisons, which means the time taken to execute the comparison varies based on the input values. This timing variation creates measurable differences that attackers can exploit through statistical analysis and repeated requests to gradually deduce the correct HMAC value. The vulnerability specifically targets the cryptographic validation process where session cookies are verified against their expected HMAC signatures, allowing attackers to reconstruct valid session tokens through systematic timing measurements.
The operational impact of this vulnerability is severe and multifaceted, providing attackers with the capability to escalate privileges and execute arbitrary code within affected applications. By successfully guessing valid session cookies through timing attacks, attackers can impersonate legitimate users and gain unauthorized access to protected application resources. This compromise can lead to full system takeover, data theft, privilege escalation, and potential lateral movement within network environments where affected applications are deployed. The vulnerability affects applications built on Ruby on Rails and other frameworks that rely on Rack for session management, creating widespread exposure across the web application ecosystem.
This vulnerability maps directly to CWE-328, which describes the weakness of using a one-way hash function in a security context where the hash function does not provide sufficient security properties such as constant-time execution. The attack pattern aligns with ATT&CK technique T1212, which involves exploiting weaknesses in cryptographic implementations to bypass authentication mechanisms. The timing attack vector demonstrates how implementation flaws in cryptographic operations can undermine even well-designed security protocols, highlighting the importance of constant-time algorithm implementations in security-critical code paths.
Mitigation strategies for CVE-2013-0263 require immediate patching of affected Rack versions to the latest stable releases that contain fixed HMAC comparison functions. Organizations should prioritize updating their Rack dependencies and verify that all applications using affected versions are properly upgraded. Additional defensive measures include implementing additional security layers such as rate limiting, monitoring for unusual timing patterns in authentication requests, and deploying intrusion detection systems that can identify potential timing attack activities. Security teams should also conduct comprehensive vulnerability assessments to identify any other applications or frameworks that might be susceptible to similar timing attack vulnerabilities in their infrastructure.