CVE-2019-1950 in UCS C-Series Rack Servers
Summary
by MITRE
A vulnerability in the firmware of the Cisco UCS C-Series Rack Servers could allow an authenticated, physical attacker to bypass Unified Extensible Firmware Interface (UEFI) Secure Boot validation checks and load a compromised software image on an affected device. The vulnerability is due to improper validation of the server firmware upgrade images. An attacker could exploit this vulnerability by installing a server firmware version that would allow the attacker to disable UEFI Secure Boot. A successful exploit could allow the attacker to bypass the signature validation checks that are done by UEFI Secure Boot technology and load a compromised software image on the affected device. A compromised software image is any software image that has not been digitally signed by Cisco.
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Analysis
by VulDB Data Team • 04/01/2024
The vulnerability identified as CVE-2019-1950 resides within the firmware implementation of Cisco UCS C-Series Rack Servers, presenting a critical security risk that undermines the fundamental integrity of the device's boot process. This flaw specifically targets the Unified Extensible Firmware Interface (UEFI) Secure Boot mechanism, which serves as the primary defense against unauthorized firmware modifications and malicious code execution during system initialization. The vulnerability stems from insufficient validation procedures applied to firmware upgrade images, creating a pathway for authenticated physical attackers to circumvent the security controls designed to protect the system's firmware integrity. The attack vector requires physical access to the device, as the vulnerability necessitates an authenticated user with administrative privileges to perform the firmware upgrade process, making it a privilege escalation issue rather than a remote attack vector. According to CWE-284, this vulnerability represents an inadequate access control mechanism within the firmware update process, while the ATT&CK framework categorizes this as a firmware modification technique under the T1542.001 sub-technique for "System Firmware" where adversaries manipulate system-level software to establish persistent backdoors or bypass security controls.
The technical exploitation of CVE-2019-1950 enables an attacker to manipulate the firmware upgrade process in a manner that disables UEFI Secure Boot functionality entirely. This occurs when an attacker installs a specifically crafted firmware version that intentionally bypasses the signature verification mechanisms inherent to UEFI Secure Boot. The compromised firmware image, once installed, allows the attacker to load any software image without proper digital signatures from Cisco, effectively nullifying the security guarantees provided by the Secure Boot technology. The vulnerability specifically affects the validation logic that should ensure all firmware images are properly signed and verified before installation, creating a scenario where malicious firmware can be installed without detection. This flaw fundamentally undermines the chain of trust that UEFI Secure Boot establishes between the hardware and the software components, allowing for the execution of unauthorized code during the boot process. The impact extends beyond simple privilege escalation as it enables the attacker to potentially establish persistent access to the system, modify core system components, and potentially gain access to sensitive data stored within the server's memory or storage subsystems.
The operational consequences of exploiting CVE-2019-1950 are severe and far-reaching for organizations relying on Cisco UCS C-Series servers for critical infrastructure operations. Once successfully exploited, the vulnerability allows attackers to establish a persistent foothold within the network that can remain undetected for extended periods, as the compromised firmware operates at a level below traditional operating system security controls. The ability to bypass UEFI Secure Boot validation creates opportunities for advanced persistent threats to deploy rootkits, backdoors, or other malicious software that can survive system reboots and traditional security scanning methods. Organizations may experience significant operational disruption, as the compromised servers can be used to conduct lateral movement attacks, data exfiltration, or serve as pivot points for attacking other systems within the network. The vulnerability also impacts the integrity of the entire system lifecycle, as any software updates or patches installed after the compromise may be rendered ineffective or even maliciously modified. This particular weakness creates a persistent threat vector that can be exploited across multiple environments, potentially affecting server clusters or entire data center infrastructures if not properly addressed through comprehensive remediation strategies.
Mitigation strategies for CVE-2019-1950 must address both immediate remediation and long-term security posture improvements to protect against exploitation of this firmware-level vulnerability. Organizations should prioritize applying the latest firmware updates provided by Cisco that specifically address the UEFI Secure Boot bypass issue, ensuring that all affected systems receive the patched firmware versions that properly validate firmware images. Network segmentation and access controls should be enhanced to limit physical access to critical servers, implementing strict authentication requirements and monitoring for unauthorized firmware modifications. The implementation of hardware security modules or trusted platform modules can provide additional layers of protection by enforcing secure boot processes and monitoring firmware integrity through cryptographic means. Regular firmware integrity checks should be implemented as part of the security monitoring process, using tools that can detect unauthorized firmware modifications or suspicious boot processes. Organizations should also consider implementing firmware-specific security solutions that can monitor for anomalous behavior patterns indicative of firmware manipulation attempts, while maintaining detailed audit logs of all firmware-related activities for forensic analysis. The security posture should include regular vulnerability assessments targeting firmware components and ensuring that physical security measures are maintained to prevent unauthorized access to server hardware, as the vulnerability requires authenticated physical access to exploit effectively.