CVE-2019-12840 in Webmin
Summary
by MITRE
In Webmin through 1.910, any user authorized to the "Package Updates" module can execute arbitrary commands with root privileges via the data parameter to update.cgi.
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Analysis
by VulDB Data Team • 12/31/2024
The vulnerability identified as CVE-2019-12840 represents a critical command injection flaw within the Webmin administrative interface that affects versions through 1.910. This security weakness resides in the Package Updates module, which is commonly used by system administrators to manage software packages on Unix and Linux systems. The vulnerability stems from insufficient input validation and sanitization within the update.cgi script, which processes user-supplied data without proper authorization checks or parameter filtering. Attackers can exploit this flaw by crafting malicious payloads through the data parameter, allowing them to execute arbitrary commands with root privileges on the affected system. The vulnerability directly maps to CWE-77 which describes improper neutralization of special elements used in command execution contexts, and aligns with ATT&CK technique T1059.001 for command and script injection.
The operational impact of this vulnerability extends far beyond simple privilege escalation, as it provides attackers with complete control over the compromised system. Once exploited, an attacker can execute any command available to the root user, potentially leading to data exfiltration, system compromise, lateral movement within the network, or establishment of persistent backdoors. The affected Webmin interface typically runs with elevated privileges to perform package management operations, making the privilege escalation path particularly dangerous. The vulnerability is particularly concerning because it requires minimal user authorization to exploit, as any user with access to the Package Updates module can leverage this flaw. This makes it an attractive target for both external attackers seeking to gain unauthorized access and internal threat actors with legitimate administrative credentials.
Mitigation strategies for CVE-2019-12840 should prioritize immediate patching of the Webmin software to version 1.920 or later, which contains the necessary fixes for this vulnerability. Organizations should implement network segmentation and access controls to limit exposure of Webmin interfaces to trusted networks only, reducing the attack surface available to potential adversaries. Additionally, implementing principle of least privilege should be enforced by restricting user access to only those modules necessary for their operational duties, particularly disabling unnecessary administrative modules. Security monitoring should include detection of suspicious command execution patterns and unusual network traffic from Webmin interfaces. The vulnerability also highlights the importance of input validation and output encoding practices in web applications, aligning with security frameworks such as OWASP Top Ten and NIST Cybersecurity Framework guidelines for preventing injection attacks. Regular security audits of web-based administrative interfaces should be conducted to identify similar vulnerabilities in other software components, as command injection flaws often occur in similar contexts where user input is not properly sanitized before being processed by system commands.