CVE-2020-12847 in Cells
Summary
by MITRE
Pydio Cells 2.0.4 web application offers an administrative console named “Cells Console� that is available to users with an administrator role. This console provides an administrator user with the possibility of changing several settings, including the application’s mailer configuration. It is possible to configure a few engines to be used by the mailer application to send emails. If the user selects the “sendmail� option as the default one, the web application offers to edit the full path where the sendmail binary is hosted. Since there is no restriction in place while editing this value, an attacker authenticated as an administrator user could force the web application into executing any arbitrary binary.
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Analysis
by VulDB Data Team • 06/05/2020
The vulnerability described in CVE-2020-12847 affects Pydio Cells 2.0.4, a web-based file sharing and collaboration platform that provides an administrative console known as Cells Console. This administrative interface is accessible only to users with administrator privileges, making it a critical component of the application's security architecture. The vulnerability stems from insufficient input validation and sanitization within the mailer configuration settings of the administrative console, specifically when configuring the sendmail binary path. The flaw exists in the application's handling of user-supplied input during the configuration process, creating a path traversal and command execution vulnerability that could be exploited by authenticated attackers.
The technical implementation of this vulnerability occurs within the administrative console's mailer configuration functionality where administrators can specify the sendmail binary path. When the sendmail option is selected as the default mailer engine, the application provides a field for editing the full path to the sendmail binary. The absence of proper validation mechanisms allows attackers to input arbitrary paths, potentially enabling them to execute malicious binaries with the privileges of the web application. This represents a classic case of insecure input handling that could lead to arbitrary code execution, as the application does not validate or sanitize the user-provided path before using it in system calls. The vulnerability is particularly dangerous because it allows an authenticated attacker to escalate their privileges and potentially gain full control over the system.
The operational impact of this vulnerability is significant, as it provides a direct path for authenticated attackers to execute arbitrary code on the target system. An attacker with administrator access could leverage this vulnerability to run malicious binaries, potentially leading to complete system compromise, data exfiltration, or lateral movement within the network. The vulnerability affects the integrity and availability of the application, as attackers could modify system configurations or install backdoors. This flaw also impacts the confidentiality of data processed by the application, as attackers could potentially intercept or manipulate email communications. The vulnerability's exploitation requires only administrative authentication, making it particularly dangerous in environments where administrative privileges are not properly restricted or monitored.
Mitigation strategies for this vulnerability should focus on implementing strict input validation and sanitization mechanisms within the administrative console. The application should validate all user-supplied paths against a whitelist of allowed binaries or implement proper path normalization to prevent directory traversal attacks. Additionally, the application should enforce proper privilege separation and use least-privilege principles when executing system commands. Security controls should include input validation at multiple levels, including client-side and server-side validation, and the application should reject any input that attempts to bypass normal path restrictions. Organizations should also implement monitoring and logging of administrative activities to detect suspicious configuration changes. This vulnerability aligns with CWE-74 and CWE-78 categories, representing weaknesses in data validation and command injection. The threat actors could potentially use techniques from the ATT&CK framework's privilege escalation and execution phases, making this vulnerability a critical target for remediation.