CVE-2020-37027: Sickbeard Alpha RCE Vulnerability

CVE-2020-37027 Overview

CVE-2020-37027 is a critical remote command injection vulnerability affecting Sickbeard alpha, a popular media management application. The vulnerability allows unauthenticated attackers to execute arbitrary commands through the extra scripts configuration feature. Attackers can set malicious commands in the extra scripts field and trigger processing to execute remote code on the vulnerable Sickbeard installation, potentially leading to complete system compromise.

Critical Impact

Unauthenticated remote command execution enables attackers to gain full control of vulnerable Sickbeard installations without requiring any credentials or user interaction.

Affected Products

• Sickbeard alpha

Discovery Timeline

• 2026-01-30 - CVE-2020-37027 published to NVD
• 2026-02-04 - Last updated in NVD database

Technical Details for CVE-2020-37027

Vulnerability Analysis

This vulnerability is classified as CWE-78 (Improper Neutralization of Special Elements used in an OS Command), commonly known as OS Command Injection. The vulnerability exists in Sickbeard's extra scripts configuration feature, which fails to properly sanitize user-supplied input before passing it to system command execution functions.

The lack of authentication on the affected endpoint combined with insufficient input validation creates a dangerous attack surface. An attacker can craft malicious input containing shell metacharacters or command sequences that will be interpreted and executed by the underlying operating system when the extra scripts functionality is triggered.

Root Cause

The root cause of this vulnerability lies in the improper handling of user-controlled input in the extra scripts configuration. The application fails to implement adequate input sanitization or validation before incorporating user-supplied data into system command execution. This allows attackers to inject arbitrary shell commands by using command separators (such as ;, |, &&, or backticks) or other shell metacharacters within the extra scripts field.

Attack Vector

The attack is network-based and requires no authentication or user interaction. An attacker can remotely access the vulnerable Sickbeard instance and manipulate the extra scripts configuration to inject malicious commands. When the application subsequently processes media files and attempts to execute the configured scripts, the injected commands are executed with the privileges of the Sickbeard process.

The attack flow involves setting a malicious payload in the extra scripts field through the application's configuration interface, then triggering the script execution mechanism (typically through media file processing). The injected commands are then executed on the host system, allowing the attacker to download additional payloads, establish reverse shells, or perform other malicious actions.

For detailed technical analysis and proof-of-concept information, refer to the Exploit-DB #48646 entry and the VulnCheck SickBeard Advisory.

Detection Methods for CVE-2020-37027

Indicators of Compromise

• Unusual process spawning from the Sickbeard application process
• Unexpected network connections originating from the Sickbeard server
• Modified extra scripts configuration containing suspicious shell commands or encoded payloads
• Presence of reverse shell connections or unusual outbound traffic on non-standard ports

Detection Strategies

• Monitor Sickbeard configuration files for unauthorized modifications to the extra scripts settings
• Implement network monitoring to detect anomalous outbound connections from the Sickbeard host
• Deploy endpoint detection solutions to identify suspicious child processes spawned by the Sickbeard application
• Review application logs for unusual configuration changes or script execution patterns

Monitoring Recommendations

• Enable comprehensive logging for all Sickbeard configuration changes
• Implement file integrity monitoring on Sickbeard configuration directories
• Configure alerting for process creation events where Sickbeard is the parent process
• Monitor for common command injection payload patterns in network traffic destined for Sickbeard instances

How to Mitigate CVE-2020-37027

Immediate Actions Required

• Restrict network access to Sickbeard instances using firewall rules to limit exposure
• Place Sickbeard behind a reverse proxy with authentication enabled
• Review and audit the extra scripts configuration for any unauthorized or suspicious entries
• Consider disabling the extra scripts functionality if not required for operations

Patch Information

Sickbeard is no longer actively maintained. Users should consider migrating to actively maintained alternatives for media management. For more information, refer to the GitHub Sick-Beard Repository and the Archived Sick-Beard Homepage.

Workarounds

• Isolate Sickbeard instances on a dedicated network segment with strict access controls
• Implement a Web Application Firewall (WAF) to filter potentially malicious input
• Run Sickbeard with minimal system privileges to limit the impact of successful exploitation
• Deploy network segmentation to prevent lateral movement if the system is compromised

# Example: Restrict Sickbeard access using iptables
# Only allow connections from trusted IP addresses
iptables -A INPUT -p tcp --dport 8081 -s 192.168.1.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 8081 -j DROP