CVE-2019-5478 in UltraScale+
Summary
by MITRE
A weakness was found in Encrypt Only boot mode in Zynq UltraScale+ devices. This could lead to an adversary being able to modify the control fields of the boot image leading to an incorrect secure boot behavior.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 11/27/2024
The vulnerability identified as CVE-2019-5478 resides within the Encrypt Only boot mode implementation of Xilinx Zynq UltraScale+ devices, representing a critical flaw in the hardware security architecture that governs secure boot processes. This weakness specifically targets the integrity verification mechanisms that protect against unauthorized modification of boot images, creating a pathway for adversaries to manipulate control fields without detection. The issue manifests in the device's inability to properly validate the authenticity and integrity of boot components, potentially allowing attackers to bypass security measures designed to prevent malicious code execution during system initialization. The vulnerability affects a broad range of Zynq UltraScale+ based systems where Encrypt Only boot mode is implemented, including embedded systems, industrial control devices, and network infrastructure equipment that rely on these processors for secure operation.
The technical flaw stems from insufficient validation of control fields within the boot image structure during the Encrypt Only boot process, which operates under the assumption that all boot components are authenticated and unmodified. This weakness allows an attacker with access to the boot environment to alter control fields that dictate the secure boot behavior, potentially enabling the execution of unauthorized code or modification of the boot process itself. The vulnerability's impact extends beyond simple code injection as it fundamentally undermines the trust model that secure boot mechanisms are designed to establish, creating opportunities for persistent backdoors or complete system compromise. The flaw operates at the hardware level within the device's boot firmware, making it particularly challenging to detect and remediate through software patches alone. According to CWE classification, this vulnerability maps to CWE-284: Improper Access Control, specifically manifesting in the context of secure boot and firmware integrity validation. The issue also aligns with ATT&CK technique T1068: Exploitation for Privilege Escalation, as successful exploitation could lead to elevated system privileges and persistent access to the affected devices.
The operational impact of CVE-2019-5478 presents significant risks to organizations deploying Zynq UltraScale+ devices in security-sensitive environments, particularly in industrial control systems, network equipment, and embedded applications where secure boot is critical for maintaining system integrity. Attackers could exploit this vulnerability to gain unauthorized access to systems, potentially leading to complete system compromise, data exfiltration, or disruption of critical operations. The vulnerability's exploitation requires access to the boot environment, making it particularly concerning for devices that operate in physically accessible locations or those that lack proper physical security measures. Organizations using affected devices may experience cascading security failures if the vulnerability allows for privilege escalation or persistent access that could remain undetected for extended periods. The long-term implications include potential compromise of entire supply chains or industrial networks where multiple affected devices exist, as the vulnerability could enable attackers to establish footholds that persist across system reboots or updates. This flaw particularly affects systems where the Encrypt Only boot mode is used as a security mechanism, undermining trust in the boot process and potentially enabling advanced persistent threats to establish lasting presence within target environments.
Mitigation strategies for CVE-2019-5478 require a multi-layered approach combining hardware and software controls to address the fundamental integrity validation flaw. Organizations should prioritize upgrading to affected devices with firmware versions that properly address the control field validation issue, though this may not be immediately available for all device variants. Implementing additional runtime protections such as memory protection units and enhanced boot monitoring can help detect unauthorized modifications to boot components, though these measures may not fully compensate for the underlying hardware vulnerability. Network segmentation and access controls should be implemented to limit physical access to affected devices, reducing the attack surface for exploitation. Regular security assessments and vulnerability scanning should be conducted to identify affected systems within the organization's infrastructure, particularly focusing on industrial control systems and embedded devices that may not receive regular security updates. The implementation of hardware security modules or trusted platform modules can provide additional layers of boot integrity verification beyond the vulnerable Encrypt Only mode. Organizations should also consider developing incident response procedures specifically addressing potential exploitation of this vulnerability, including protocols for system recovery and forensic analysis. According to industry best practices, this vulnerability should be treated as a critical security concern requiring immediate assessment and remediation planning, as the potential for persistent system compromise makes it a high-priority target for exploitation by advanced threat actors.