CVE-2019-5672 in Linux for Tegra
Summary
by MITRE
NVIDIA Linux for Tegra (L4T) contains a vulnerability where the Secure Shell (SSH) keys provided in the sample rootfs are not replaced by unique host keys after sample rootsfs generation and flashing, which may lead to information disclosure. The updates apply to all versions prior to and including R28.3.
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Analysis
by VulDB Data Team • 05/29/2020
The vulnerability identified as CVE-2019-5672 affects NVIDIA Linux for Tegra (L4T) systems, specifically targeting the Secure Shell (SSH) key implementation within the sample root filesystem. This security flaw stems from the improper handling of host keys during the system provisioning process, where default SSH keys remain unchanged after the initial rootfs generation and flashing operations. The issue impacts all versions of NVIDIA L4T prior to and including R28.3, creating a persistent security risk that extends across multiple generations of embedded Linux systems. The vulnerability represents a critical weakness in the system's initial security posture, as it provides attackers with pre-configured authentication credentials that should have been unique to each deployment.
The technical root cause of this vulnerability lies in the failure to implement proper host key generation mechanisms during the sample rootfs creation process. When NVIDIA provides sample root filesystems for Tegra-based systems, they include default SSH host keys that are meant to be replaced with unique identifiers specific to each target device. However, the current implementation does not enforce this replacement process, leaving the default keys in place. This flaw directly maps to CWE-310, which addresses cryptographic weaknesses in key management, specifically the use of default or predictable cryptographic keys. The vulnerability creates a scenario where any attacker who gains access to one device's default SSH keys can potentially access other systems using identical default keys, effectively breaking the security isolation between different deployments.
The operational impact of this vulnerability extends beyond simple credential exposure, creating significant risks for embedded systems deployed in sensitive environments. When default SSH keys remain unchanged across multiple devices, it enables attackers to perform reconnaissance and lateral movement attacks with minimal initial effort. The vulnerability affects the principle of least privilege and undermines the security model of the system, as it allows unauthorized access to devices that should be individually secured. This weakness particularly impacts industrial control systems, automotive applications, and other embedded environments where Tegra processors are commonly deployed, potentially leading to complete system compromise. The vulnerability also aligns with ATT&CK technique T1566, which covers the use of default credentials for initial access, and T1078, which addresses valid accounts for persistence.
Mitigation strategies for CVE-2019-5672 require immediate action to address the root cause of the issue. System administrators must ensure that all sample root filesystems are properly configured with unique SSH host keys before deployment, implementing automated processes that generate fresh host keys during the flashing or provisioning process. The recommended approach involves integrating host key generation into the standard deployment workflow, ensuring that each device receives unique cryptographic identifiers during the initial setup. Organizations should also implement monitoring systems to detect any attempts to use default credentials, as well as establish procedures for regular security assessments of deployed systems. The vulnerability highlights the importance of following secure configuration practices and implementing proper key management procedures, which aligns with security standards such as NIST SP 800-53 and ISO 27001 requirements for cryptographic key management. Additionally, deploying network segmentation and access controls can help limit the potential impact of compromised default keys, while regular security updates and patches should be applied to ensure that newer versions of NVIDIA L4T properly address this issue.