CVE-2021-47796: Denver SHC-150 Camera RCE Vulnerability

CVE-2021-47796 Overview

CVE-2021-47796 is a critical hardcoded credentials vulnerability affecting the Denver SHC-150 Smart Wifi Camera. This IoT security flaw allows unauthenticated remote attackers to gain full shell access to the camera's underlying Linux operating system by connecting to the exposed telnet service on port 23 using default credentials embedded in the device firmware.

The vulnerability stems from CWE-798 (Use of Hard-coded Credentials), a common but severe security weakness in IoT devices where manufacturers embed static authentication credentials into device firmware. Attackers who discover these credentials can compromise any device running the vulnerable firmware without requiring prior authentication.

Critical Impact

Unauthenticated attackers can achieve full remote code execution on the Denver SHC-150 camera, enabling complete device takeover, surveillance manipulation, network pivoting, and potential botnet recruitment.

Affected Products

• Denver SHC-150 Smart Wifi Camera
• Denver Smart Home Security Camera Series (Indoor IP Camera)

Discovery Timeline

• January 16, 2026 - CVE-2021-47796 published to NVD
• January 16, 2026 - Last updated in NVD database

Technical Details for CVE-2021-47796

Vulnerability Analysis

This vulnerability represents a fundamental security design flaw where the Denver SHC-150 camera ships with an accessible telnet service and hardcoded authentication credentials. The telnet daemon listens on TCP port 23 and accepts connections using credentials that are identical across all devices running the affected firmware version.

Once authenticated, attackers obtain a Linux shell with elevated privileges, granting them the ability to execute arbitrary commands on the device's operating system. This level of access enables attackers to view or record video feeds, modify device configurations, install persistent backdoors, disable security features, or leverage the compromised camera as a launching point for attacks against other devices on the local network.

The attack requires no user interaction and can be performed remotely over the network. The simplicity of exploitation—requiring only a telnet client and knowledge of the default credentials—makes this vulnerability particularly dangerous for internet-exposed devices.

Root Cause

The root cause of CVE-2021-47796 is the use of hardcoded credentials (CWE-798) in the Denver SHC-150 firmware. Rather than implementing a secure credential provisioning mechanism that requires users to set unique passwords during device setup, the manufacturer embedded static credentials directly into the firmware. This practice violates fundamental IoT security principles and leaves all deployed devices vulnerable to credential-based attacks.

Additionally, the telnet service itself presents a security concern as it transmits credentials and data in plaintext, making it susceptible to network sniffing attacks even if credentials were not hardcoded.

Attack Vector

The attack vector is network-based with no authentication requirements. An attacker can exploit this vulnerability by:

1. Identifying a Denver SHC-150 camera accessible on the network (locally or internet-exposed)
2. Connecting to TCP port 23 (telnet service) on the target device
3. Authenticating using the hardcoded default credentials
4. Executing arbitrary commands on the underlying Linux operating system

The attack complexity is low, requiring no special privileges, no user interaction, and no sophisticated techniques. Network scanning tools can easily identify devices with open telnet ports, and once the hardcoded credentials are publicly known, mass exploitation becomes trivial.

Technical details and proof-of-concept information are available through the Exploit-DB entry #50160 and the VulnCheck Advisory.

Detection Methods for CVE-2021-47796

Indicators of Compromise

• Unexpected telnet connections (TCP port 23) to Denver SHC-150 cameras from external or unusual internal IP addresses
• Successful authentication events on the camera's telnet service followed by command execution
• Modified system files, new user accounts, or unexpected processes running on the camera
• Unusual network traffic originating from the camera, including connections to unknown external hosts

Detection Strategies

• Deploy network monitoring to detect telnet traffic (port 23) to and from IoT devices on the network
• Implement intrusion detection rules to alert on telnet connection attempts to known camera IP addresses
• Monitor for credential-based attacks using default or common IoT credentials
• Use asset discovery tools to identify all Denver cameras and IoT devices with exposed telnet services

Monitoring Recommendations

• Establish baseline network behavior for IoT devices and alert on deviations
• Monitor DNS queries from camera devices for suspicious domain lookups
• Configure SIEM rules to correlate telnet access attempts with post-exploitation indicators
• Regularly audit IoT device firmware versions and exposed services

How to Mitigate CVE-2021-47796

Immediate Actions Required

• Isolate Denver SHC-150 cameras on a dedicated network segment (VLAN) with restricted internet access
• Block inbound and outbound telnet traffic (TCP port 23) at the network firewall level
• Audit all Denver cameras on the network and assess their exposure to this vulnerability
• Consider replacing affected devices with cameras from vendors with stronger security practices

Patch Information

No vendor patch information is currently available for this vulnerability. Denver has not released a firmware update to address the hardcoded credential issue. Users should consult the Denver Smart Home Camera product page for any future security updates.

Workarounds

• Block telnet (TCP port 23) access to the camera using network firewalls or access control lists
• Place affected cameras behind a NAT gateway without port forwarding to prevent direct internet exposure
• Implement network segmentation to isolate IoT devices from critical network resources
• Deploy network-based intrusion prevention systems (IPS) to detect and block exploitation attempts
• If the device supports it, attempt to disable the telnet service through the camera's configuration interface

# Example firewall rule to block telnet access to IoT devices
# Replace 192.168.1.100 with your camera's IP address

# iptables example (Linux router/firewall)
iptables -A FORWARD -d 192.168.1.100 -p tcp --dport 23 -j DROP
iptables -A INPUT -s 192.168.1.100 -p tcp --sport 23 -j DROP

# Block all telnet traffic on the network
iptables -A FORWARD -p tcp --dport 23 -j DROP