CVE-2006-4246 in Usermin
Summary
by MITRE
Usermin before 1.220 (20060629) allows remote attackers to read arbitrary files, possibly related to chfn/save.cgi not properly handling an empty shell parameter, which results in changing root s shell instead of the shell of a specified user.
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Analysis
by VulDB Data Team • 07/20/2019
The vulnerability identified as CVE-2006-4246 affects Usermin versions prior to 1.220, specifically dating back to June 29, 2006, and represents a critical privilege escalation flaw that enables remote attackers to read arbitrary files on affected systems. This vulnerability resides within the chfn/save.cgi component of Usermin, which is part of the broader Virtualmin suite of web-based system administration tools. The flaw manifests when the system fails to properly validate or sanitize the shell parameter provided during user account modification operations, creating a pathway for malicious actors to manipulate system-level configurations. The vulnerability directly relates to CWE-22, which describes improper limitation of a pathname to a restricted directory, and CWE-79, which addresses cross-site scripting vulnerabilities that can be exploited to manipulate system behavior through crafted input parameters. The core technical issue stems from the improper handling of empty shell parameters within the chfn/save.cgi script, where the application does not adequately validate user input before executing system commands or modifying critical configuration files. When an attacker submits an empty shell parameter, the system incorrectly interprets this as a directive to modify the root user's shell configuration instead of the intended target user's shell, effectively allowing unauthorized access to system-level resources. This misconfiguration creates a privilege escalation vector that can be exploited to gain elevated system privileges, potentially leading to complete system compromise. The operational impact of this vulnerability extends beyond simple file reading capabilities, as it fundamentally undermines the integrity of user account management within the system. Attackers can leverage this flaw to access sensitive system files, potentially including password files, configuration data, and other critical system resources that should remain protected. The vulnerability is particularly concerning because it operates through a legitimate administrative interface, making it difficult to detect through traditional network monitoring approaches. The flaw can be exploited remotely without requiring authentication, which significantly amplifies its potential impact and makes it an attractive target for automated exploitation tools. The security implications align with ATT&CK technique T1068, which covers 'Exploitation for Privilege Escalation' and T1566, which addresses 'Phishing for Information', as attackers can use this vulnerability to gain deeper system access and extract sensitive information from compromised systems. Systems running vulnerable versions of Usermin are at heightened risk of unauthorized access and data breaches, particularly in environments where administrative interfaces are exposed to untrusted networks. The vulnerability demonstrates a classic example of insecure input handling and privilege management, where the application fails to properly validate user-provided parameters against expected input formats and system security boundaries. Remediation efforts must include immediate patching to Usermin version 1.220 or later, along with comprehensive review of system configurations to ensure that administrative interfaces are properly secured and isolated from external threats. Network segmentation and access control measures should be implemented to limit exposure of administrative interfaces, while regular security audits should verify that all system components are properly updated and configured according to security best practices. Organizations should also consider implementing additional monitoring and detection capabilities to identify potential exploitation attempts targeting similar vulnerabilities in their infrastructure.