CVE-2021-27942 in P65-F1
Summary
by MITRE • 08/03/2021
Vizio P65-F1 6.0.31.4-2 and E50x-E1 10.0.31.4-2 Smart TVs allow a threat actor to execute arbitrary code from a USB drive via the Smart Cast functionality, because files on the USB drive are effectively under the web root and can be executed.
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Analysis
by VulDB Data Team • 08/07/2021
The vulnerability identified as CVE-2021-27942 affects Vizio Smart TVs models P65-F1 and E50x-E1 running specific firmware versions, presenting a critical security flaw that enables remote code execution through USB drive insertion. This vulnerability resides within the Smart Cast functionality of these devices, which is designed to facilitate wireless content streaming and device connectivity. The flaw stems from improper file handling and access control mechanisms that fail to properly isolate user-accessible storage from the system's web root directory structure.
The technical implementation of this vulnerability exploits the lack of proper file system segmentation between user-inserted USB content and the web server's document root. When a USB drive is inserted into the affected Smart TV, the device automatically scans and processes files stored on the drive without adequate sanitization or access restriction measures. Files placed on the USB drive can be executed directly through the web interface, effectively allowing threat actors to place malicious code in locations that are automatically served by the web server. This creates a direct execution path from user-controllable storage to system-level code execution, bypassing normal security boundaries that should separate user data from system processes.
The operational impact of this vulnerability extends beyond simple remote code execution, as it provides attackers with persistent access to the device's underlying system. Once successfully exploited, threat actors can gain full control over the Smart TV's operating system, potentially enabling them to install additional malware, modify system configurations, or establish persistent backdoors. The vulnerability is particularly concerning because it requires minimal user interaction beyond inserting a USB drive, making it suitable for social engineering attacks or automated exploitation campaigns. This flaw represents a significant compromise of the device's security model and can potentially be leveraged to create a network of compromised Smart TVs that could be used for further attacks or surveillance activities.
Mitigation strategies for this vulnerability should focus on implementing proper file system access controls and web root isolation mechanisms. Device manufacturers should ensure that user-inserted content is properly sandboxed and cannot directly execute code within the web server context. Network segmentation and access control measures should be implemented to prevent unauthorized code execution from external storage devices. The vulnerability aligns with CWE-22 Improper Limitation of a Pathname to a Restricted Directory and CWE-74 Improper Neutralization of Special Elements in Output Used by a Downstream Component, and follows ATT&CK techniques including T1059 Command and Scripting Interpreter and T1078 Valid Accounts for maintaining persistent access. Users should immediately update to patched firmware versions when available and avoid inserting unknown USB drives into Smart TV devices to prevent exploitation of this critical vulnerability.