Overview
CVE-2018-25126 exposes a significant security vulnerability within the firmware of Shenzhen TVT Digital Technology Co., Ltd. NVMS-9000. This firmware is commonly utilized in various white-labeled Digital Video Recorder (DVR), Network Video Recorder (NVR), and Internet Protocol Camera (IPC) products. The vulnerability stems from two primary issues: the presence of hardcoded API credentials and an OS command injection flaw within the configuration services. This allows for unauthenticated remote attackers to gain arbitrary command execution as root.
Technical Details
The NVMS-9000 web/API interface accepts HTTP/XML requests. Authentication is bypassed using a fixed vendor credential string, a hardcoded value present within the firmware. User-controlled fields are then passed into shell execution contexts without proper sanitization. This lack of input validation allows an attacker to inject shell metacharacters inside XML parameters. By exploiting endpoints such as /editBlackAndWhiteList, attackers can achieve arbitrary command execution with root privileges.
The same vulnerable backend is also accessible through a proprietary TCP service on port 4567 in some models. This service accepts a magic GUID preface and base64-encoded XML, allowing the command injection sink to be reached in a different manner.
According to reports, firmware releases from mid-February 2018 onward address this vulnerability. The Shadowserver Foundation observed exploitation evidence on 2025-01-28 UTC.
CVSS Analysis
CVSS score is not available. However, due to the combination of unauthenticated access, hardcoded credentials, and root-level command execution, the vulnerability is regarded as critical.
Possible Impact
The impact of CVE-2018-25126 is severe. Successful exploitation allows an attacker to:
- Gain complete control over the affected device.
- Access and exfiltrate sensitive video and audio data.
- Modify device configurations, potentially disabling security features.
- Use the compromised device as a bot in a botnet (as seen in the Juniper Networks report).
- Compromise the network to which the device is connected, potentially leading to further attacks.
Mitigation and Patch Steps
The primary mitigation is to update the firmware to a version released after mid-February 2018. If an update is not available or feasible, consider the following:
- Isolate the affected devices on a separate network segment.
- Implement strong firewall rules to restrict access to port 4567 and the web interface.
- Monitor network traffic for suspicious activity, such as unauthorized access attempts to the vulnerable endpoints.
- Consider replacing the device with a more secure alternative if a patch is not available.
