CVE-2018-12434 in LibreSSL
Summary
by MITRE
LibreSSL before 2.6.5 and 2.7.x before 2.7.4 allows a memory-cache side-channel attack on DSA and ECDSA signatures, aka the Return Of the Hidden Number Problem or ROHNP. To discover a key, the attacker needs access to either the local machine or a different virtual machine on the same physical host.
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Analysis
by VulDB Data Team • 02/19/2020
The vulnerability identified as CVE-2018-12434 represents a critical memory-cache side-channel attack affecting LibreSSL versions prior to 2.6.5 and 2.7.x versions before 2.7.4. This security flaw exploits the inherent characteristics of cryptographic implementations that process DSA and ECDSA signatures, creating a pathway for attackers to extract sensitive key information through sophisticated cache analysis techniques. The vulnerability is particularly concerning as it leverages the Return Of the Hidden Number Problem (ROHNP) methodology, which has been previously documented in cryptographic literature and represents a sophisticated approach to key recovery attacks.
The technical implementation of this vulnerability stems from how LibreSSL handles cryptographic operations within memory caches during signature generation processes. When DSA and ECDSA algorithms process signatures, they perform operations that leave observable patterns in cache behavior, which can be exploited by attackers with sufficient access privileges. The attack requires either local machine access or access to a different virtual machine running on the same physical host, making this vulnerability particularly dangerous in cloud computing environments where multiple tenants share the same hardware infrastructure. This access requirement aligns with the common threat model described in the attack mitigation framework, where attackers with local privileges or those capable of executing code on shared hardware can exploit the cache timing side-channel.
The operational impact of CVE-2018-12434 extends beyond simple key exposure, as it fundamentally undermines the security assumptions of cryptographic implementations that rely on cache-optimized operations. Attackers can potentially recover private keys used for digital signatures, which would compromise the authenticity and integrity of signed communications, certificates, and cryptographic operations. This vulnerability particularly affects systems using LibreSSL for TLS/SSL operations, certificate management, and digital signature validation where the underlying cryptographic libraries are susceptible to cache-based attacks. The implications are severe for organizations relying on these cryptographic implementations for securing sensitive communications and data integrity.
Mitigation strategies for this vulnerability require immediate patching of affected LibreSSL versions to the recommended secure releases, specifically updating to LibreSSL 2.6.5 or 2.7.4 and later. Organizations should also implement additional security measures such as cache eviction techniques, memory access randomization, and virtual machine isolation to reduce the attack surface. The vulnerability demonstrates the importance of considering side-channel attacks in cryptographic implementation design, as outlined in the CWE catalog under category 310 for cryptographic side channels. Security teams should also consider implementing monitoring for suspicious cache access patterns and regularly audit cryptographic implementations for potential vulnerabilities that could be exploited through similar side-channel attacks. This vulnerability serves as a reminder of the ongoing challenges in securing cryptographic implementations against sophisticated attack vectors that exploit implementation details rather than fundamental algorithm weaknesses.