CVE-2018-20106 in yast2-printer
Summary
by MITRE
In yast2-printer up to and including version 4.0.2 the SMB printer settings don't escape characters in passwords properly. If a password with backticks or simliar characters is supplied this allows for executing code as root. This requires tricking root to enter such a password in yast.
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Analysis
by VulDB Data Team • 08/01/2023
The vulnerability identified as CVE-2018-20106 affects the yast2-printer package version 4.0.2 and earlier, representing a critical security flaw in the handling of SMB printer authentication credentials. This issue stems from inadequate input sanitization within the printer configuration interface, specifically when processing password values containing special characters. The flaw enables arbitrary code execution with root privileges, making it particularly dangerous in enterprise environments where administrative access is frequently required. The vulnerability operates through a command injection vector that exploits improper escaping of characters in password fields during SMB printer setup processes.
The technical implementation of this vulnerability involves the insecure handling of backtick characters and similar special symbols within password strings. When users enter passwords containing these characters through the yast2-printer interface, the system fails to properly escape these inputs before processing them in shell contexts. This creates a command injection opportunity where maliciously crafted passwords can execute arbitrary commands with elevated privileges. The vulnerability is classified under CWE-78 as a failure to properly escape shell metacharacters, specifically targeting the improper handling of command line arguments. Attackers can leverage this weakness by crafting passwords that contain backticks, dollar signs, or other shell metacharacters that get interpreted by the underlying shell during printer configuration operations.
The operational impact of CVE-2018-20106 extends beyond simple privilege escalation to encompass complete system compromise when attackers can influence user behavior. The vulnerability requires social engineering to trick a root user into entering a malicious password through the yast interface, but once executed, it provides attackers with full root access to the system. This attack vector aligns with ATT&CK technique T1068 which covers "Exploitation for Privilege Escalation" and specifically addresses how adversaries can leverage application flaws to gain elevated privileges. The attack chain typically involves an attacker first gaining access to a user account with sufficient privileges to configure printers, then crafting a malicious password that when entered triggers the command injection. The vulnerability affects systems where yast2-printer is installed and used for printer management, particularly those running SUSE Linux Enterprise Server or openSUSE distributions.
Mitigation strategies for CVE-2018-20106 must address both immediate remediation and long-term security hardening. The primary solution involves upgrading to yast2-printer version 4.0.3 or later, which contains proper input sanitization and character escaping mechanisms. Organizations should implement immediate patch management procedures to ensure all affected systems receive updates promptly. Additionally, administrators should consider implementing network segmentation to limit access to printer configuration interfaces and reduce the attack surface. The vulnerability demonstrates the importance of proper input validation and output encoding in security-critical applications, reinforcing principles from the OWASP Top 10 that emphasize secure input handling and protection against injection attacks. System administrators should also monitor for suspicious printer configuration activities and implement logging controls that can detect anomalous behavior related to printer setup operations, as this vulnerability could be exploited through legitimate administrative access.