CVE-2020-25082 in Trusted Platform Module
Summary
by MITRE • 08/10/2021
An attacker with physical access to Nuvoton Trusted Platform Module (NPCT75x 7.2.x before 7.2.2.0) could extract an Elliptic Curve Cryptography (ECC) private key via a side-channel attack against ECDSA, because of an Observable Timing Discrepancy.
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Analysis
by VulDB Data Team • 08/15/2021
The vulnerability CVE-2020-25082 represents a critical security flaw in Nuvoton Trusted Platform Module devices, specifically affecting the NPCT75x series with firmware versions prior to 7.2.2.0. This issue arises from a fundamental weakness in the cryptographic implementation that exposes the system to sophisticated side-channel attacks. The vulnerability is particularly concerning because it can be exploited by adversaries who have physical access to the target device, making it a significant risk for embedded systems where physical security cannot be guaranteed. The affected hardware implements the Trusted Platform Module specification, which is designed to provide secure cryptographic operations and key storage mechanisms that are essential for protecting sensitive data and maintaining system integrity.
The technical root cause of this vulnerability lies in an observable timing discrepancy during ECDSA (Elliptic Curve Digital Signature Algorithm) operations within the cryptographic processor. This timing variation creates a side-channel attack vector that allows an attacker to infer information about the private key through careful analysis of execution time differences. The vulnerability specifically affects the implementation of elliptic curve cryptography operations, where the cryptographic processor's response time varies based on the input values during signature generation. According to CWE-385, this represents a timing attack vulnerability where the attacker can exploit the correlation between the execution time and the secret data being processed. The attacker can measure these timing variations through precise monitoring equipment and use statistical analysis to reconstruct the private key components, effectively breaking the cryptographic protection mechanisms that should safeguard the key material.
The operational impact of this vulnerability extends far beyond simple cryptographic compromise, as it fundamentally undermines the trust model that TPM devices are designed to provide. When an attacker successfully extracts an ECC private key, they gain the ability to forge digital signatures, decrypt sensitive communications, and impersonate legitimate system components within the security domain. This compromise affects the core security guarantees of the TPM, including the integrity verification of system boot processes, secure key storage, and authentication mechanisms. The vulnerability is particularly dangerous in environments where physical access is possible, such as industrial control systems, embedded devices, or IoT deployments where attackers might gain direct access to hardware components. From an ATT&CK framework perspective, this vulnerability maps to techniques involving credential access through side-channel attacks and privilege escalation via compromised cryptographic keys, potentially enabling further lateral movement within networks where these devices are integrated.
Mitigation strategies for CVE-2020-25082 primarily focus on firmware updates and hardware-level security improvements. The most effective immediate solution is upgrading to Nuvoton firmware version 7.2.2.0 or later, which implements proper constant-time cryptographic operations to eliminate the timing discrepancies. Organizations should conduct comprehensive inventory assessments to identify all affected NPCT75x devices within their infrastructure and prioritize remediation efforts accordingly. Additional protective measures include implementing physical security controls to prevent unauthorized access to affected hardware, deploying monitoring systems to detect potential side-channel attack attempts, and considering alternative cryptographic implementations that are inherently resistant to timing attacks. The vulnerability highlights the importance of designing cryptographic systems with side-channel resistance as a fundamental requirement rather than an afterthought, aligning with industry best practices outlined in NIST SP 800-57 and other cryptographic standards that emphasize the need for constant-time implementations to prevent information leakage through timing variations.