CVE-2021-47745

Vulnerability

Analysis

An authenticated command injection vulnerability (CWE-78) exists in the Cypress Solutions CTM-200 industrial cellular wireless gateway, version 2.7.1 (and also 2.0.5.3356-184). The flaw resides in the firmware upgrade functionality, specifically within the /www/cgi-bin/webif/ctm-config-upgrade.sh script. When a user triggers a firmware upgrade via the web form, the script passes the user-supplied fw_url POST parameter directly to the cmd upgradefw command (line 139). The underlying ELF binary cmdmain constructs a command string using sprintf() and then passes it to ctmsys(), which executes it via execv(). The fw_url value is not sanitized, allowing an attacker to inject arbitrary shell metacharacters into the wget command that is executed [1][2][4].

Exploitation

The vulnerability requires prior authentication to the CTM-200's web interface, as an admin-level user. An attacker with valid credentials can craft a POST request to the firmware upgrade CGI endpoint. The fw_url parameter, intended to hold a URL for downloading a firmware image, can instead contain command injection payloads, such as appending ; or | followed by shell commands. Because the injected commands are executed in the context of the ctmsysitem() function call—which itself runs with root privileges—the attacker gains full control over the gateway. The exploit is classified as 'semi-blind' because while the output may not be directly returned in the HTTP response, commands are executed and their effects can be observed or they can exfiltrate data through outbound connections [2].

Impact

Successful exploitation grants the attacker remote, interactive shell access with root privileges on the CTM-200 device. This enables complete compromise of the gateway, including the ability to modify configuration, intercept or redirect network traffic, access connected SCADA systems, and use the device as a persistent pivot point into the broader industrial network. Given that the CTM-200 is used in mobile fleet applications and fixed-site industrial communications, this represents a high-severity threat to operational technology environments [1][2][3].

Mitigation

The vulnerability was publicly disclosed on September 21, 2021, and an exploit is publicly available on Exploit-DB. Users should immediately check with Cypress Solutions for a patched firmware version (none was indicated as available at the time of disclosure). As a workaround, restrict administrative access to the CTM-200 web interface by network segmentation and use strong, unique passwords. Because the device may be deployed in critical infrastructure, the vulnerability should be prioritized for remediation and monitored for inclusion in CISA's Known Exploited Vulnerabilities (KEV) catalog [2][4].