CVE-2022-25213 in Das U-Boot
Summary
by MITRE • 03/10/2022
Improper physical access control and use of hard-coded credentials in /etc/passwd permits an attacker with physical access to obtain a root shell via an unprotected UART port on the device. The same port exposes an unauthenticated Das U-Boot BIOS shell.
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Analysis
by VulDB Data Team • 03/12/2022
This vulnerability represents a critical security flaw in embedded systems that combines physical access control failures with hardcoded credential exploitation to enable unauthorized root access. The issue manifests through improper physical access controls that fail to adequately protect sensitive system interfaces, specifically exposing a UART port that lacks proper authentication mechanisms. The combination of hard-coded credentials in the /etc/passwd file with an unprotected bootloader interface creates a multi-layered attack vector that significantly weakens the system's security posture.
The technical implementation of this vulnerability leverages the fundamental principle that physical access to embedded devices can bypass traditional network-based security controls. When an attacker gains physical access to the device, they can connect to the UART port and utilize the unauthenticated Das U-Boot BIOS shell to execute commands with elevated privileges. This exploitation pathway directly violates the principle of least privilege and demonstrates how hardcoded credentials in system configuration files can provide persistent access vectors. The vulnerability aligns with CWE-798, which specifically addresses the use of hard-coded credentials, and CWE-284, which covers improper access control mechanisms.
The operational impact of CVE-2022-25213 extends beyond simple privilege escalation to encompass complete system compromise and potential data exfiltration. Attackers can leverage this vulnerability to establish persistent backdoors, modify system binaries, install malicious software, or extract sensitive information from the device. The exposure of the U-Boot shell provides attackers with direct access to the boot process, enabling them to modify bootloader configurations or replace system firmware components. This level of access represents a severe threat to device integrity and can compromise the security of entire network infrastructures if multiple devices share similar configurations.
Mitigation strategies should focus on implementing proper physical security controls including securing UART ports through hardware modifications or disabling unused interfaces. System administrators must eliminate hardcoded credentials by implementing dynamic credential management and regular credential rotation. The U-Boot configuration should be hardened to require authentication for shell access, and physical access controls should be enforced through tamper-evident mechanisms. Organizations should also implement network segmentation and monitoring to detect unauthorized physical access attempts. This vulnerability demonstrates the importance of following security guidelines from the NIST Cybersecurity Framework and aligns with ATT&CK technique T1211 for lateral movement through physical access, emphasizing the need for comprehensive security postures that address both digital and physical attack surfaces.