CVE-2015-2079 in Usermin
Summary
by MITRE • 04/28/2025
Usermin 0.980 through 1.x before 1.660 allows uconfig_save.cgi sig_file_free remote code execution because it uses the two argument (not three argument) form of Perl open.
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Analysis
by VulDB Data Team • 05/15/2025
The vulnerability identified as CVE-2015-2079 represents a critical remote code execution flaw in Usermin versions ranging from 0.980 through 1.x before 1.660. This vulnerability specifically targets the uconfig_save.cgi component within the Usermin web-based administration interface, which is commonly used for managing user accounts and system configurations on Unix-like operating systems. The flaw stems from improper handling of file operations within Perl scripting, creating a dangerous condition that can be exploited by remote attackers to execute arbitrary code on affected systems. The vulnerability's impact is particularly severe given that Usermin is often deployed in environments where it provides administrative access to multiple users, making it a prime target for exploitation.
The technical root cause of this vulnerability lies in the improper use of Perl's open function with only two arguments instead of the recommended three-argument form. When Perl's open function is called with two arguments, it implicitly interprets the second argument as a shell command, effectively bypassing normal file access controls and allowing arbitrary command execution. This pattern violates fundamental security principles and creates a path for command injection attacks. The specific function sig_file_free within uconfig_save.cgi demonstrates this flaw by accepting user-supplied input and passing it directly to the two-argument open call without proper sanitization or validation. This design pattern aligns with CWE-78, which describes improper neutralization of special elements used in OS commands, and represents a classic example of shell injection vulnerability. The vulnerability operates at the application level and can be exploited through web-based interfaces, making it particularly dangerous in environments where Usermin is accessible from untrusted networks.
The operational impact of this vulnerability extends beyond simple code execution, as it allows attackers to gain full administrative control over affected systems. Successful exploitation can lead to complete system compromise, data exfiltration, privilege escalation, and persistent backdoor installation. Attackers can leverage this vulnerability to modify system configurations, create new user accounts, access sensitive files, and potentially use the compromised system as a launching point for further attacks within the network. The vulnerability affects systems where Usermin is installed and accessible, particularly those running older versions that have not received the security patch. Given that Usermin is commonly deployed on web servers and system administration platforms, the potential attack surface is broad, encompassing various organizational environments from small businesses to large enterprises. This vulnerability also demonstrates the importance of proper input validation and secure coding practices, as the flaw could have been easily prevented by using the three-argument form of Perl's open function which explicitly separates the file handle from the command string.
Mitigation strategies for CVE-2015-2079 focus primarily on patching the affected software to the latest secure versions where the vulnerability has been addressed. Organizations should immediately upgrade to Usermin version 1.660 or later, which contains the necessary fixes for this vulnerability. In addition to patching, system administrators should implement network segmentation and access controls to limit exposure of Usermin interfaces to trusted networks only. The three-argument form of Perl's open function should be enforced throughout the codebase to prevent similar issues in the future, aligning with secure coding guidelines and best practices. Additional defensive measures include implementing web application firewalls to monitor for suspicious requests, conducting regular security audits of web applications, and ensuring that all third-party software components are kept up to date with security patches. Organizations should also consider implementing monitoring solutions to detect unusual system activity that might indicate exploitation attempts, and establish incident response procedures specifically addressing remote code execution vulnerabilities. The vulnerability serves as a reminder of the critical importance of secure coding practices and the potential consequences of seemingly minor implementation flaws in security-critical applications.