CVE-2016-7440 in MySQL Server
Summary
by MITRE
The C software implementation of AES Encryption and Decryption in wolfSSL (formerly CyaSSL) before 3.9.10 makes it easier for local users to discover AES keys by leveraging cache-bank timing differences.
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Analysis
by VulDB Data Team • 09/27/2022
The vulnerability identified as CVE-2016-7440 affects the wolfSSL cryptographic library implementation of AES encryption and decryption algorithms. This issue resides in the C software implementation of AES operations within wolfSSL, which was previously known as CyaSSL, and impacts versions prior to 3.9.10. The flaw represents a significant security concern as it exposes cryptographic keys through side-channel analysis techniques that exploit timing variations in cache memory access patterns. The vulnerability specifically targets the cache-bank timing differences that occur during AES operations, making it possible for local attackers to perform cache timing attacks against the cryptographic implementation.
The technical flaw manifests through cache timing side-channel attacks that exploit the differential timing behavior of cache memory banks during AES encryption and decryption processes. When the AES algorithm processes data, it accesses memory locations in patterns that can be observed through timing measurements. The cache-bank timing differences create observable variations in execution time that correlate with the cryptographic key material being processed. Attackers can leverage these timing variations to reconstruct AES keys through statistical analysis of multiple encryption or decryption operations. This type of vulnerability falls under the category of cache timing attacks, which are well-documented in cybersecurity literature and represent a common class of side-channel attacks that exploit physical implementation characteristics rather than algorithmic weaknesses.
The operational impact of this vulnerability is substantial for systems utilizing affected versions of wolfSSL, particularly in environments where local privilege escalation is possible or where attackers have access to the same system. Local users with access to the target system can potentially extract AES keys used for encryption and decryption operations, which compromises the confidentiality of all data protected by those keys. The vulnerability affects not only the cryptographic security of the system but also potentially impacts the integrity and availability of services that depend on proper encryption. Organizations using wolfSSL for secure communications, SSL/TLS implementations, or cryptographic operations are at risk, as the extracted keys could be used to decrypt sensitive data or impersonate legitimate services within the network.
Mitigation strategies for CVE-2016-7440 primarily involve upgrading to wolfSSL version 3.9.10 or later, which contains patches addressing the cache timing vulnerabilities. Additionally, organizations should implement proper cryptographic implementation practices that include cache timing attack resistance mechanisms such as constant-time algorithm implementations and memory access pattern randomization. The mitigation approach aligns with industry standards and best practices for side-channel attack prevention, including recommendations from the National Institute of Standards and Technology and other cybersecurity frameworks. System administrators should also consider implementing monitoring and detection mechanisms to identify potential cache timing attack activities. The vulnerability demonstrates the importance of proper cryptographic implementation security and the necessity of considering side-channel attack vectors during the development and deployment of cryptographic libraries. This issue highlights the need for comprehensive security testing that includes side-channel vulnerability assessment and the application of defense-in-depth strategies to protect against various attack vectors including timing-based side-channel attacks.