CVE-2017-11756 in Ear Music
Summary
by MITRE
In Earcms Ear Music through 4.1 build 20170710, remote authenticated users can execute arbitrary PHP code by changing the allowable music-upload extensions to include .php in addition to .mp3 and .m4a in admin.php?iframe=config_upload, and then using user.php/music/add/ to upload the code.
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Analysis
by VulDB Data Team • 11/02/2019
The vulnerability identified as CVE-2017-11756 affects Earcms Ear Music version 4.1 build 20170710, representing a critical security flaw in the content management system's file upload functionality. This issue manifests as a lack of proper input validation and sanitization within the administrative interface, specifically in the configuration handling for music file uploads. The vulnerability stems from the application's failure to adequately restrict file extensions that can be uploaded, creating an avenue for malicious code execution through seemingly legitimate administrative functions.
The technical exploitation of this vulnerability occurs through a specific sequence of actions that leverage the application's administrative interface. Attackers with valid authentication credentials can navigate to the admin.php?iframe=config_upload endpoint and modify the allowable file extensions to include .php in addition to the standard .mp3 and .m4a formats. This modification effectively transforms the upload functionality from a legitimate file handling mechanism into a code execution vector. The vulnerability is classified under CWE-434, which specifically addresses "Upload of Code" where the application allows users to upload files that are subsequently executed as code.
The operational impact of this vulnerability is severe and multifaceted, as it enables authenticated attackers to execute arbitrary PHP code on the affected server. This capability allows for complete system compromise, data exfiltration, and potential lateral movement within the network. The vulnerability's exploitation requires only legitimate administrative credentials, making it particularly dangerous as it bypasses many traditional perimeter security controls. Once exploited, attackers can establish persistent backdoors, modify application behavior, and potentially use the compromised system as a launch point for further attacks against other systems within the organization.
The attack pattern follows established methodologies documented in the MITRE ATT&CK framework, specifically mapping to techniques involving command and control through file upload operations. The vulnerability enables adversaries to achieve initial access and maintain persistence through code execution, while also potentially facilitating privilege escalation and defense evasion. Organizations using this version of Earcms are particularly vulnerable because the flaw exists in the core upload configuration logic rather than in a specific module, making it difficult to isolate and remediate without comprehensive application review.
Mitigation strategies for CVE-2017-11756 should focus on immediate patching of the application to version 4.2 or later, which addresses the file extension validation issue. Administrators should implement additional security controls including restricting file upload functionality to specific user roles, implementing strict file type validation with whitelisting approaches, and ensuring proper file extension checks at both the application and web server levels. Network segmentation and monitoring of file upload activities should be implemented to detect anomalous behavior. The vulnerability highlights the importance of proper input validation and secure coding practices, particularly when dealing with user-supplied data in web applications. Organizations should also consider implementing web application firewalls and regular security assessments to identify similar issues in other applications within their infrastructure.