CVE-2017-7622 in DDE
Summary
by MITRE
dde-daemon, the daemon process of DDE (Deepin Desktop Environment) 15.0 through 15.3, runs with root privileges and hardly does anything to identify the user who calls the function through D-Bus. Anybody can change the grub config, even to append some arguments to make a backdoor or privilege escalation, by calling DoWriteGrubSettings() provided by dde-daemon.
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Analysis
by VulDB Data Team • 08/28/2020
The vulnerability identified as CVE-2017-7622 resides within the dde-daemon component of the Deepin Desktop Environment version 15.0 through 15.3, representing a critical privilege escalation flaw that fundamentally undermines system security. This daemon process operates with elevated root privileges while maintaining insufficient authentication mechanisms for D-Bus function calls, creating a dangerous attack surface where unauthorized users can exploit the lack of proper access controls. The vulnerability specifically manifests through the DoWriteGrubSettings() function, which allows arbitrary modification of the GRUB bootloader configuration without proper user verification or privilege checking, effectively enabling any local or remote attacker to execute malicious code with system-level privileges.
The technical exploitation of this vulnerability stems from the daemon's failure to implement proper authentication and authorization checks when processing D-Bus requests. According to CWE-284, this represents an improper access control vulnerability where the system grants privileges to unauthorized entities through insufficient verification mechanisms. The dde-daemon process runs with root privileges but fails to validate the identity or authorization level of callers attempting to invoke the DoWriteGrubSettings() function, creating a direct path for privilege escalation. This flaw directly maps to ATT&CK technique T1068, which describes the exploitation of legitimate credentials and privileges to gain system-level access through local privilege escalation methods.
The operational impact of this vulnerability is severe and far-reaching, as it provides attackers with the capability to modify the GRUB bootloader configuration, which serves as a critical system component for boot process initialization. An attacker could append malicious kernel parameters or modify boot configurations to establish persistent backdoors, effectively compromising the entire system's integrity and security posture. The vulnerability's exploitation does not require elevated privileges initially, as the daemon itself runs with root access, making the attack surface particularly dangerous for desktop environments where users might not be fully aware of the underlying system security implications. This flaw essentially allows an attacker to modify system boot parameters that could result in privilege escalation, persistent access, or complete system compromise.
Mitigation strategies for CVE-2017-7622 should focus on implementing proper authentication mechanisms within the dde-daemon process and restricting D-Bus access to authorized users only. The most effective approach involves modifying the daemon to validate caller identity and authorization levels before executing the DoWriteGrubSettings() function, implementing proper input validation, and reducing the daemon's privilege level where possible. Organizations should also implement D-Bus access control lists that restrict which users or processes can invoke the vulnerable function, and consider applying the principle of least privilege by ensuring the daemon only operates with necessary privileges. Additionally, system administrators should monitor D-Bus traffic for suspicious activity and implement proper logging mechanisms to detect potential exploitation attempts, as outlined in the NIST Cybersecurity Framework's detection and protection controls. The vulnerability highlights the importance of proper privilege separation and access control implementation in desktop environment components, emphasizing that even seemingly benign system services can represent critical security risks when not properly secured.