CVE-2019-3929

What Are Crestron Devices?

Crestron manufactures audiovisual and building control systems — touch panels, media processors, room controllers — widely deployed in corporate conference rooms, government facilities, universities, and executive offices to manage displays, audio, lighting, and video conferencing. These devices are frequently network-connected for remote management and are often deployed with default configurations, making an unauthenticated remote code execution flaw in their embedded web interface especially dangerous: a compromised AV controller can serve as a stealthy foothold or covert audio/video surveillance point inside otherwise well-secured facilities.

Overview

CVE-2019-3929 is a critical, unauthenticated command injection vulnerability affecting multiple Crestron product lines, reachable via the file_transfer.cgi HTTP endpoint on the device's embedded web server. A remote attacker with no credentials can execute arbitrary operating system commands with root privileges, giving full control of the affected device. CVSS score: 9.8.

Technical Details

The file_transfer.cgi handler processes parameters related to file transfer operations on the device without adequately sanitizing them before passing them to a system shell. By embedding shell metacharacters in a request to this endpoint, an attacker can inject arbitrary OS commands that execute with root privileges — the level at which the embedded web server process runs on this class of device. No authentication, no user interaction, and no complex attack chain is required: a single crafted HTTP request against the exposed CGI endpoint is sufficient for full device compromise.

Discovery

This vulnerability was addressed through Crestron's standard security advisory and patch process.

Exploitation Context

CISA's KEV addition confirms this vulnerability has been exploited in the wild. Unauthenticated root command injection in a widely deployed AV control device is a high-value target: compromise can enable persistent network access inside conference rooms and executive spaces, and in worst-case scenarios, abuse of connected microphones/cameras for covert surveillance, in addition to standard risks like using the device as a network pivot point.

Remediation

1. Apply the Crestron firmware update that addresses CVE-2019-3929 for all affected product models.
2. Never expose Crestron device web interfaces directly to the internet — restrict access to trusted management VLANs only.
3. Inventory all Crestron and other AV/building-control devices on the network, since these systems are frequently deployed by facilities or AV integration teams outside normal IT asset management processes.
4. Segment AV/IoT control systems from corporate and sensitive networks using VLANs and firewall rules.
5. Review device logs and configuration for signs of prior compromise, including unexpected file transfers or configuration changes via file_transfer.cgi.