Attack Chain

1. Attacker downloads the publicly available NVR_4H firmware image (V27.5.58.6) from Tenda.
2. Attacker unpacks the firmware container using standard tools (e.g., binwalk, unsquashfs).
3. Attacker extracts the hardcoded private key (/etc/privkey.pem) and certificate (/etc/cacert.pem) from the squashfs partition.
4. Attacker positions themselves on the network segment as the NVR_4H administrator (via ARP spoofing or DNS poisoning).
5. Attacker intercepts the TLS connection between the admin's browser and the NVR using the extracted private key to decrypt and present the legitimate-looking certificate.
6. Attacker performs real-time traffic manipulation to capture administrator credentials, session tokens, and camera RTSP credentials.
7. Attacker gains unauthorized administrative access to the recorder and connected surveillance cameras.

Impact

Successful exploitation results in the complete loss of confidentiality and integrity for the HTTPS management interface. An attacker can perform a passive man-in-the-middle attack to harvest credentials or modify system configuration, granting full control over the surveillance infrastructure.

Recommendation

• Identify all Tenda NVR_4H units within the environment and confirm their firmware version.
• Isolate vulnerable NVR_4H devices from untrusted network segments or external exposure until a patch is available.
• Implement strict network segmentation to minimize the risk of ARP spoofing or MITM attacks targeting management traffic.
• Monitor for unauthorized ARP traffic or anomalous network configuration changes within segments hosting NVR devices.
• Contact Tenda support to inquire about firmware updates or patches that remove the hardcoded key material and implement per-device provisioning.