CVE-2018-18930 in Digital Signage
Summary
by MITRE
The Tightrope Media Carousel digital signage product 7.0.4.104 contains an arbitrary file upload vulnerability in the Manage Bulletins/Upload feature, which can be leveraged to gain remote code execution. An authenticated attacker can upload a crafted ZIP file (based on an exported backup of existing "Bulletins") containing a malicious file. When uploaded, the system only checks for the presence of the needed files within the ZIP and, as long as the malicious file is named properly, will extract all contained files to a new directory on the system, named with a random GUID. The attacker can determine this GUID by previewing an image from the uploaded Bulletin within the web UI. Once the GUID is determined, the attacker can navigate to the malicious file and execute it. In testing, an ASPX web shell was uploaded, allowing for remote-code execution in the context of a restricted IIS user.
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Analysis
by VulDB Data Team • 01/29/2024
The Tightrope Media Carousel digital signage product version 7.0.4.104 presents a critical arbitrary file upload vulnerability that fundamentally compromises system security through the Manage Bulletins/Upload feature. This vulnerability represents a classic insecure file handling flaw that allows authenticated attackers to bypass intended security controls and execute malicious code remotely. The vulnerability stems from inadequate validation of uploaded files, specifically when processing ZIP archives that contain bulletin data exports. The system's file processing logic focuses solely on verifying the presence of required files within the archive without implementing proper content inspection or file type validation, creating an exploitable gap in the security model.
The technical implementation of this vulnerability exploits a fundamental flaw in the application's file extraction and deployment mechanism. When an attacker uploads a crafted ZIP file containing malicious content, the system performs minimal validation checks that only confirm the existence of expected files within the archive structure. The system then extracts all contained files to a randomly generated directory named with a GUID, which serves as an obfuscation mechanism but does not provide actual security. This extraction process occurs without proper file type filtering or content analysis, allowing malicious files to be placed in the filesystem alongside legitimate content. The random GUID generation provides only superficial protection, as attackers can determine the directory path by previewing images from the uploaded bulletin through the web interface, effectively bypassing any intended security measures.
The operational impact of this vulnerability extends far beyond simple unauthorized file placement, as it provides complete remote code execution capabilities within the context of a restricted IIS user account. This represents a significant escalation from a simple file upload vulnerability to a full remote command execution threat, allowing attackers to establish persistent access, escalate privileges, and potentially compromise the entire digital signage network. The vulnerability affects the broader digital signage ecosystem by exposing critical infrastructure components to unauthorized access, potentially enabling attackers to manipulate content, disrupt services, or use compromised systems as launch points for further attacks against connected networks. The restricted IIS user context limits immediate privilege escalation but still provides access to system resources and potential lateral movement opportunities within the network environment.
The vulnerability aligns with CWE-434, which specifically addresses "Unrestricted Upload of File with Dangerous Type," and demonstrates how inadequate input validation and file handling can create exploitable conditions for remote code execution. From an ATT&CK perspective, this vulnerability maps to T1190 for exploit public-facing application and T1059 for command and scripting interpreter, representing both initial access and execution phases of an attack lifecycle. The threat actor can leverage this vulnerability to establish persistent access through the deployment of web shells, which can be used for ongoing monitoring, data exfiltration, or further network infiltration. Organizations using this digital signage solution face significant risk of unauthorized content manipulation, service disruption, and potential compromise of sensitive information displayed through the signage systems.
Mitigation strategies must address both the immediate vulnerability and broader security posture of the affected systems. The primary recommendation involves implementing strict file type validation and content inspection mechanisms that prevent execution-capable files from being uploaded and processed. Organizations should deploy proper input validation that verifies file contents, not just extensions, and implement proper access controls that limit upload capabilities to authorized personnel only. Network segmentation and monitoring should be implemented to detect and prevent unauthorized file uploads and subsequent execution attempts. Regular security updates and patches should be applied immediately upon availability, while also conducting thorough vulnerability assessments of similar digital signage products and systems. The implementation of web application firewalls and file integrity monitoring solutions can provide additional layers of protection against exploitation attempts, while comprehensive logging and alerting should be established to detect suspicious upload activities and potential exploitation attempts.