CVE-2016-6882 in MatrixSSL
Summary
by MITRE
MatrixSSL before 3.8.7, when the DHE_RSA based cipher suite is supported, makes it easier for remote attackers to obtain RSA private key information by conducting a Lenstra side-channel attack.
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Analysis
by VulDB Data Team • 09/03/2020
The vulnerability described in CVE-2016-6882 represents a critical security flaw in MatrixSSL versions prior to 3.8.7 that specifically affects implementations using DHE_RSA cipher suites. This weakness stems from insufficient protection against side-channel attacks, particularly those targeting the mathematical operations involved in Diffie-Hellman key exchange with RSA authentication. The vulnerability exposes sensitive cryptographic information through timing variations that can be exploited by remote attackers to reconstruct RSA private keys. The attack vector operates through the Lenstra side-channel attack methodology, which leverages observable timing differences in cryptographic computations to infer secret information. This particular implementation flaw creates a significant risk for systems relying on MatrixSSL for secure communications, as the exposure of RSA private keys would compromise the entire cryptographic infrastructure and enable attackers to impersonate legitimate services or decrypt previously captured communications.
The technical root cause of this vulnerability lies in the improper implementation of cryptographic operations within the MatrixSSL library, specifically when handling DHE_RSA cipher suites. The cryptographic library fails to implement constant-time operations during the modular exponentiation processes required for Diffie-Hellman key exchanges, creating timing variations that can be measured and analyzed by attackers. According to CWE-327, this vulnerability relates to the use of weak or broken cryptographic algorithms and implementations, while the side-channel attack methodology aligns with ATT&CK technique T1583.001 for acquiring infrastructure and T1071.004 for application layer protocol. The vulnerability affects the cryptographic primitive implementation by not properly masking the computational timing patterns that reveal information about the private key components, making the system susceptible to sophisticated attacks that require only network access and the ability to observe timing variations in cryptographic operations.
The operational impact of this vulnerability extends beyond immediate cryptographic compromise to encompass broader security implications for affected systems. Once an attacker successfully extracts RSA private keys through this side-channel attack, they gain the ability to decrypt secure communications, forge digital signatures, and impersonate services within the compromised network. The vulnerability affects any system utilizing MatrixSSL with DHE_RSA cipher suites, which includes numerous web servers, email servers, and other network services that rely on this cryptographic library for secure communications. Organizations may face regulatory compliance violations, reputational damage, and potential legal consequences from data breaches resulting from this vulnerability. The attack requires minimal resources and can be executed remotely, making it particularly dangerous for systems with public exposure. The vulnerability also impacts the trust model of the affected systems, as the compromise of private keys undermines the fundamental security assumptions that cryptographic protocols rely upon for maintaining confidentiality and integrity.
Mitigation strategies for CVE-2016-6882 primarily focus on upgrading to MatrixSSL version 3.8.7 or later, which implements proper countermeasures against side-channel attacks. Organizations should immediately disable DHE_RSA cipher suites if they are not actively required for legacy compatibility, as this removes the attack surface entirely. Implementing constant-time cryptographic operations and ensuring proper randomization of computational timing are essential defensive measures that align with industry best practices outlined in NIST SP 800-57 and ISO/IEC 14443. Network segmentation and monitoring for unusual timing variations in cryptographic operations can help detect potential exploitation attempts. Additionally, organizations should conduct comprehensive vulnerability assessments to identify all systems using affected MatrixSSL versions and ensure proper patch management procedures are in place to prevent similar vulnerabilities from arising in the future. The implementation of these mitigations should be coordinated with existing security frameworks such as ISO 27001 and NIST Cybersecurity Framework to maintain comprehensive security posture and compliance requirements.