CVE-2020-36829 in Mojolicious Module
Summary
by MITRE • 04/08/2024
The Mojolicious module before 8.65 for Perl is vulnerable to secure_compare timing attacks that allow an attacker to guess the length of a secret string. Only versions after 1.74 are affected.
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Analysis
by VulDB Data Team • 08/26/2024
The Mojolicious web framework for perl contains a critical timing attack vulnerability in its secure_compare function that enables attackers to determine the length of secret strings through careful analysis of response times. This vulnerability affects versions prior to 8.65 and represents a significant weakness in the framework's cryptographic operations. The issue stems from the implementation of the secure_compare function which is designed to prevent timing attacks but inadvertently leaks information about string lengths through timing variations. When comparing secret values such as session tokens, API keys, or authentication hashes, the function's behavior reveals statistical patterns that can be exploited by attackers to reconstruct the secret data.
The technical flaw manifests in the secure_compare implementation where the comparison process does not maintain constant execution time regardless of input differences. This timing variation occurs because the function processes inputs sequentially and terminates early when mismatches are detected, creating measurable delays that correlate with the length of matching prefixes. Attackers can exploit this by measuring response times for multiple comparison attempts with varying input lengths, thereby inferring the length of the target secret string through statistical analysis. This vulnerability directly relates to CWE-203, which addresses the exposure of sensitive information through timing variations, and represents a classic example of how cryptographic implementations can introduce side-channel attacks despite intended security measures.
The operational impact of this vulnerability extends beyond simple information disclosure to potentially enable more sophisticated attacks including session hijacking, authentication bypasses, and credential compromise. When attackers can determine the length of secret strings, they significantly reduce the search space for brute force attacks and can optimize their guessing strategies. This weakness particularly affects web applications that rely on Mojolicious for authentication mechanisms, session management, or API security where secret tokens are compared using the vulnerable function. The vulnerability affects applications handling sensitive data such as user authentication tokens, cryptographic keys, or secure session identifiers, making it a critical concern for security-conscious organizations.
Mitigation strategies for this vulnerability require immediate upgrading to Mojolicious version 8.65 or later where the secure_compare function has been properly implemented to maintain constant execution time regardless of input differences. Organizations should also conduct thorough code reviews to identify any custom implementations of similar comparison functions that might exhibit the same timing characteristics. Additionally, implementing additional security layers such as rate limiting, multi-factor authentication, and proper input validation can help reduce the attack surface. Security teams should monitor their applications for any timing-based anomalies and consider implementing more robust cryptographic libraries that inherently prevent timing attacks. This vulnerability highlights the importance of following established security practices and the need for thorough testing of cryptographic implementations against side-channel attacks as recommended by the ATT&CK framework's technique T1212 for exploitation of cryptographic weaknesses.