CVE-2019-3937 in AM-100
Summary
by MITRE
Crestron AM-100 with firmware 1.6.0.2 and AM-101 with firmware 2.7.0.2 stores usernames, passwords, slideshow passcode, and other configuration options in cleartext in the file /tmp/scfgdndf. A local attacker can use this vulnerability to recover sensitive data.
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Analysis
by VulDB Data Team • 09/11/2023
The CVE-2019-3937 vulnerability affects Crestron AM-100 and AM-101 devices running specific firmware versions, presenting a critical security flaw in how sensitive configuration data is stored. This vulnerability resides in the device's handling of authentication credentials and access controls, where the system fails to implement proper encryption or obfuscation mechanisms for sensitive information. The flaw is particularly concerning as it allows local attackers to directly access and extract confidential data from a specific file path, creating a significant attack surface for unauthorized personnel with physical or network access to the device.
The technical implementation of this vulnerability stems from the device's insecure storage practices where all authentication-related information including usernames, passwords, slideshow passcodes, and other configuration options are persistently stored in cleartext format within the /tmp/scfgdndf file. This represents a direct violation of security best practices and falls under the category of insecure data storage as defined by CWE-312. The /tmp directory is typically used for temporary file storage, but in this case, it serves as an insecure repository for critical system information. The cleartext storage approach provides no protection against unauthorized access, making the vulnerability easily exploitable by any local user who can read the file contents.
The operational impact of this vulnerability extends beyond simple credential theft, as it compromises the entire security posture of the affected Crestron devices. Local attackers with minimal privileges can exploit this flaw to gain access to authentication credentials that may be reused across multiple systems, potentially enabling lateral movement within network environments. The vulnerability undermines the device's ability to maintain confidentiality and integrity of sensitive configuration data, creating potential for privilege escalation attacks and unauthorized access to connected systems. This flaw particularly affects enterprise environments where Crestron devices are used for control and automation, as the stolen credentials could provide access to building management systems, security infrastructure, and other critical network components.
From a threat modeling perspective, this vulnerability aligns with ATT&CK technique T1552.001 for unsecured credentials and T1078.004 for valid accounts. The attack surface is limited to local access but represents a significant risk in environments where physical security is inadequate or where attackers have already gained initial access through other vectors. Organizations should consider implementing additional security controls such as file system permissions, regular monitoring of temporary directories, and network segmentation to limit the impact of such vulnerabilities. The vulnerability also highlights the importance of secure configuration management and proper data sanitization practices in embedded systems. Remediation efforts should include firmware updates from Crestron, immediate file system hardening, and implementation of proper access controls to prevent unauthorized file system access. Organizations using these devices should conduct comprehensive security assessments to identify similar insecure storage practices in other system components and implement proper encryption mechanisms for all sensitive data at rest.