CVE-2018-12438 in Elliptic Curve Cryptography library
Summary
by MITRE
The Elliptic Curve Cryptography library (aka sunec or libsunec) allows a memory-cache side-channel attack on ECDSA signatures, aka the Return Of the Hidden Number Problem or ROHNP. To discover an ECDSA 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-2018-12438 represents a critical side-channel attack against the elliptic curve cryptography implementation within the Java runtime environment. This flaw specifically affects the sunec library, which provides elliptic curve cryptographic operations including ECDSA signature generation and verification. The vulnerability stems from a memory-cache timing side-channel that enables attackers to extract private ECDSA keys through careful analysis of cache access patterns during cryptographic operations. This attack vector is particularly concerning because it exploits the inherent timing differences in memory cache behavior during cryptographic computations, allowing adversaries to reconstruct sensitive private keys from public signatures.
The technical implementation of this vulnerability leverages the Return Of the Hidden Number Problem (ROHNP) attack methodology, which builds upon earlier research into hidden number problems in cryptographic contexts. The flaw occurs within the ECDSA signature process where the cryptographic library performs operations that leave detectable traces in the CPU cache hierarchy. When the sunec library executes ECDSA signature operations, it accesses memory locations in patterns that vary based on the private key bits being processed. An attacker with sufficient access privileges can monitor these cache access patterns and correlate them with the mathematical operations performed during signature generation. This creates a timing channel that leaks information about the private key through cache behavior rather than direct cryptographic analysis.
The operational impact of CVE-2018-12438 is significant for systems running vulnerable Java implementations, particularly those utilizing ECDSA for digital signatures, TLS certificates, or code signing operations. Attackers can exploit this vulnerability from either local system access or through a compromised virtual machine running on the same physical host, making it particularly dangerous in cloud computing environments and containerized deployments. The attack requires minimal privileges and can be executed without requiring direct access to the cryptographic keys themselves, making it a stealthy threat that can persist undetected while gradually extracting key material. Organizations using Java-based applications for security-sensitive operations face substantial risk as the compromised keys could enable impersonation, certificate forgery, and unauthorized access to protected systems.
Mitigation strategies for this vulnerability focus on both immediate remediation and architectural considerations. The primary solution involves updating to patched versions of the Java runtime environment where Oracle has addressed the memory cache timing issues in the sunec library implementation. Additionally, organizations should implement virtualization security measures such as CPU cache isolation, memory access controls, and hypervisor-level protections to prevent cross-VM attacks. The vulnerability aligns with CWE-310, which addresses cryptographic weakness in memory access patterns, and relates to ATT&CK techniques involving credential access through side-channel attacks. Organizations should also consider implementing cryptographic key rotation procedures and monitoring for unusual cache access patterns that might indicate exploitation attempts. Network segmentation and principle of least privilege access controls further reduce the attack surface and limit potential damage from successful exploitation.