CVE-2020-8948 in Windows Mobile Broadband Driver Package
Summary
by MITRE
The Sierra Wireless Windows Mobile Broadband Driver Packages (MBDP) before build 5043 allows an unprivileged user to overwrite arbitrary files in arbitrary folders using hard links. An unprivileged user could leverage this vulnerability to execute arbitrary code with system privileges.
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Analysis
by VulDB Data Team • 04/16/2020
The vulnerability identified as CVE-2020-8948 affects the Sierra Wireless Windows Mobile Broadband Driver Packages MBDP software version prior to build 5043. This represents a critical privilege escalation flaw that stems from improper file handling mechanisms within the driver installation and management processes. The vulnerability specifically manifests when the software creates files without proper validation of the target directory structure, creating opportunities for malicious exploitation through symbolic link manipulation techniques.
The technical root cause of this vulnerability lies in the insecure creation of hard links during file operations within the driver package management system. When the vulnerable software processes driver installation or update procedures, it fails to properly validate or sanitize the target paths where files are created, allowing unprivileged users to manipulate the file creation process through hard link attacks. This flaw falls under the category of improper file handling and path validation as classified by CWE-22 and CWE-73 respectively. The vulnerability enables attackers to create hard links in strategic locations that will be overwritten by subsequent file operations, effectively allowing arbitrary file overwrite conditions.
The operational impact of this vulnerability is severe as it provides a pathway for privilege escalation from unprivileged user accounts to system-level privileges. An attacker with low-privilege access to a Windows system running the vulnerable MBDP software can exploit this flaw to overwrite critical system files or binaries with malicious content. The exploitation process typically involves creating a hard link to a target file in a location that will be subsequently overwritten by the driver installation process, thereby allowing the attacker to inject malicious code that will execute with elevated privileges. This attack vector directly aligns with techniques described in the MITRE ATT&CK framework under privilege escalation tactics and techniques.
The vulnerability creates a persistent threat model where successful exploitation results in complete system compromise. Once an attacker achieves system-level execution through this privilege escalation, they gain full control over the affected Windows system, including the ability to install additional malware, modify system configurations, exfiltrate data, or establish persistence mechanisms. The attack requires minimal prerequisites beyond local access to the system, making it particularly dangerous in environments where user accounts may be compromised or where insider threats exist. Organizations running affected Sierra Wireless MBDP software versions should immediately implement mitigation strategies including patching to build 5043 or later, restricting user privileges where possible, and monitoring for suspicious file creation patterns in system directories.
Security practitioners should note that this vulnerability demonstrates the importance of proper file handling security practices, particularly in driver and system-level software components. The flaw underscores the need for implementing proper access controls, input validation, and secure file creation practices to prevent attackers from manipulating file system operations. The vulnerability serves as a reminder that even seemingly benign system components like driver packages can contain critical security flaws that enable significant privilege escalation attacks. Organizations should conduct comprehensive vulnerability assessments to identify other potentially vulnerable software components and ensure that all system drivers and packages are regularly updated to address known security issues.