CVE-2018-12437 in LibTomCrypt
Summary
by MITRE
LibTomCrypt through 1.18.1 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 • 06/05/2026
The vulnerability identified as CVE-2018-12437 represents a critical memory-cache side-channel attack targeting the LibTomCrypt cryptographic library version 1.18.1 and earlier. This flaw exploits the Return Of the Hidden Number Problem (ROHNP) to compromise ECDSA (Elliptic Curve Digital Signature Algorithm) key security. The attack mechanism leverages cache timing information that can be observed through memory access patterns, making it particularly dangerous in shared computing environments where multiple virtual machines operate on the same physical hardware. The vulnerability specifically affects cryptographic implementations that use the libtomcrypt library for ECDSA signature generation, creating a pathway for attackers to extract sensitive private key information through careful analysis of cache behavior during cryptographic operations.
The technical implementation of this vulnerability stems from the way the ECDSA signature algorithm handles memory operations during computation, particularly in how it manages the scalar multiplication process on elliptic curves. When cryptographic operations are performed, the library accesses memory locations in patterns that can be correlated with cache hit/miss behaviors, which reveal information about the secret scalar value being used. This occurs because the cryptographic implementation does not properly randomize memory access patterns or mask the timing characteristics of the computations. The attack specifically targets the hidden number problem where an attacker can recover the secret scalar by observing sufficient signature operations and analyzing the resulting cache behavior. This technique represents a sophisticated application of side-channel analysis that falls under the broader category of cache-based side-channel attacks.
The operational impact of this vulnerability is severe and particularly concerning in cloud computing and virtualized environments where multiple tenants share the same physical infrastructure. An attacker with access to either the local machine or a different virtual machine running on the same physical host can systematically gather cache timing information to reconstruct the ECDSA private key. The attack requires only a moderate amount of signature data to be collected, making it practical for real-world exploitation. This vulnerability undermines the fundamental security assumptions of elliptic curve cryptography implementations, as it demonstrates that even mathematically sound cryptographic algorithms can be compromised through implementation flaws that expose information through side channels. The implications extend beyond simple key recovery, potentially enabling full compromise of systems relying on ECDSA for authentication, digital signatures, and certificate validation.
Mitigation strategies for CVE-2018-12437 require both immediate library updates and implementation-level protections. The most effective immediate solution involves upgrading to LibTomCrypt version 1.18.2 or later, which contains patches addressing the cache timing vulnerabilities. Organizations should also implement countermeasures such as constant-time algorithm implementations, memory access randomization, and cache flushing techniques to prevent information leakage through side channels. Additionally, system administrators should consider isolating cryptographic operations on dedicated hardware when possible, or implementing virtualization security controls that prevent cross-VM cache attacks. From a compliance perspective, this vulnerability aligns with CWE-310 (Cryptographic Implementation Fault) and represents a significant concern for organizations following security frameworks such as NIST SP 800-57 and ISO/IEC 15408 (Common Criteria) that mandate proper protection against side-channel attacks. The attack vector also maps to ATT&CK technique T1059.001 (Command and Scripting Interpreter) and T1552.001 (Unsecured Credentials) in the context of how attackers might leverage such vulnerabilities to escalate privileges or compromise additional systems through credential theft.