CVE-2020-36915: Adtec Digital SignEdje Auth Bypass Flaw

CVE-2020-36915 Overview

CVE-2020-36915 is a hardcoded credentials vulnerability affecting Adtec Digital SignEdje Digital Signage Player v2.08.28. The device contains multiple hardcoded default credentials that allow unauthenticated remote access to web, telnet, and SSH interfaces. Attackers can exploit these credentials to gain root-level access and execute system commands across multiple Adtec Digital product versions.

This vulnerability falls under CWE-798 (Use of Hard-coded Credentials), a critical security flaw where authentication credentials are embedded directly in the firmware or source code, making them difficult to change and easy for attackers to discover and exploit.

Critical Impact

Unauthenticated attackers can gain root-level access to affected digital signage systems via network-accessible services (web, telnet, SSH), potentially compromising display content, network infrastructure, and sensitive organizational data.

Affected Products

• Adtec Digital SignEdje Digital Signage Player v2.08.28
• Other Adtec Digital product versions with shared firmware
• Digital signage deployments using default configurations

Discovery Timeline

• 2026-01-06 - CVE CVE-2020-36915 published to NVD
• 2026-01-08 - Last updated in NVD database

Technical Details for CVE-2020-36915

Vulnerability Analysis

The vulnerability stems from the use of hardcoded default credentials within the Adtec Digital SignEdje Digital Signage Player firmware. These credentials are accessible across multiple administrative interfaces including the web management console, telnet service, and SSH daemon. Because the credentials are hardcoded into the device firmware, they cannot be easily changed by end users, and any attacker who discovers them—through reverse engineering, public disclosure, or exploit databases—can authenticate to any affected device exposed on the network.

Digital signage players are often deployed in public or semi-public locations with network connectivity, making them attractive targets for attackers seeking initial access to corporate networks or looking to display unauthorized content. The availability of root-level access through these hardcoded credentials significantly amplifies the potential impact, as attackers gain complete control over the device operating system.

Root Cause

The root cause of this vulnerability is insecure firmware development practices where authentication credentials were embedded directly into the device software rather than requiring unique credentials to be set during initial device configuration. This approach was likely implemented for ease of manufacturing or deployment but creates a systemic security weakness across all devices sharing the same firmware version.

The hardcoded credentials exist in multiple service configurations (web server, telnet daemon, SSH daemon), indicating a pattern of insecure default configuration throughout the device's administrative interfaces. This design flaw violates fundamental security principles of credential management and secure-by-default configurations.

Attack Vector

The attack vector for CVE-2020-36915 is network-based and requires no user interaction or prior authentication. An attacker with network access to an affected device can:

1. Identify the target device through network scanning or Shodan/Censys searches for exposed digital signage systems
2. Attempt authentication using the known default credentials against the web interface (typically HTTP/HTTPS)
3. Alternatively, connect via telnet or SSH using the same hardcoded credentials
4. Upon successful authentication, gain root-level command execution capabilities

The exploitation process is straightforward and does not require advanced technical skills. Public exploit code and credential details are available through resources such as Exploit-DB #48954 and Zero Science Vulnerability ZSL-2020-5603.

Once authenticated, attackers can modify display content, pivot to other network systems, install persistent backdoors, or disrupt signage operations entirely.

Detection Methods for CVE-2020-36915

Indicators of Compromise

• Unexpected authentication attempts or successful logins to Adtec Digital SignEdje management interfaces from unknown IP addresses
• SSH or telnet sessions originating from external networks to digital signage devices
• Modification of display content or configuration files without authorized administrator action
• New user accounts or SSH keys added to the device
• Unusual outbound network connections from digital signage systems

Detection Strategies

• Implement network monitoring to alert on telnet (port 23) and SSH (port 22) connections to digital signage devices from non-administrative networks
• Review web server access logs for authentication attempts using default usernames
• Deploy honeypot credentials or canary files on signage devices to detect unauthorized access
• Use vulnerability scanners to identify exposed Adtec Digital devices with default credential configurations

Monitoring Recommendations

• Enable comprehensive logging on all administrative interfaces of digital signage systems
• Configure SIEM alerts for authentication events involving known default credential usernames
• Monitor network traffic for lateral movement originating from digital signage device IP addresses
• Perform regular asset inventory scans to identify exposed Adtec Digital devices on internal and external networks

How to Mitigate CVE-2020-36915

Immediate Actions Required

• Identify all Adtec Digital SignEdje Digital Signage Player devices deployed in your environment
• Immediately change all default credentials on web, telnet, and SSH interfaces where possible
• Disable telnet service entirely and restrict SSH access to specific administrative IP addresses
• Segment digital signage devices onto isolated network VLANs with restricted internet access
• Block external access to administrative ports (22, 23, 80, 443) on signage devices at the firewall level

Patch Information

At the time of publication, no vendor-supplied patch information is available in the CVE data. Organizations should contact Adtec Digital directly for firmware updates that address hardcoded credential vulnerabilities. Review the VulnCheck Adtec Digital Advisory and IBM X-Force Vulnerability #190628 for additional technical details and remediation guidance.

Workarounds

• Implement network segmentation to isolate digital signage devices from critical infrastructure and restrict management access to authorized administrator workstations only
• Deploy a jump host or VPN requirement for all administrative access to signage systems
• If credential changes are not supported by the firmware, consider replacing affected devices with alternatives that support proper credential management
• Implement additional authentication layers such as network-level authentication or certificate-based access where supported

# Network isolation configuration example (iptables)
# Restrict SSH access to management VLAN only
iptables -A INPUT -p tcp --dport 22 -s 192.168.100.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 22 -j DROP

# Block telnet entirely
iptables -A INPUT -p tcp --dport 23 -j DROP

# Restrict web interface access
iptables -A INPUT -p tcp --dport 80 -s 192.168.100.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -s 192.168.100.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP
iptables -A INPUT -p tcp --dport 443 -j DROP