CVE-2020-37026: Sickbeard Alpha CSRF Vulnerability

CVE-2020-37026 Overview

CVE-2020-37026 is a Cross-Site Request Forgery (CSRF) vulnerability affecting Sickbeard alpha, a popular open-source PVR application for managing TV shows. The vulnerability allows remote attackers to disable authentication by tricking authenticated users into submitting crafted configuration parameters. When exploited, attackers can clear web username and password settings, effectively removing authentication protection from the application.

Critical Impact

Successful exploitation allows attackers to disable authentication on Sickbeard instances, potentially exposing the application and its data to unauthorized access.

Affected Products

• Sickbeard alpha (all versions)

Discovery Timeline

• 2026-01-30 - CVE CVE-2020-37026 published to NVD
• 2026-02-04 - Last updated in NVD database

Technical Details for CVE-2020-37026

Vulnerability Analysis

This vulnerability stems from the lack of proper CSRF token validation in the Sickbeard web configuration interface. The application fails to implement anti-CSRF mechanisms to verify that state-changing requests originate from legitimate user sessions. As a result, attackers can craft malicious web pages or links that, when visited by an authenticated Sickbeard administrator, automatically submit requests to modify critical authentication settings.

The attack requires user interaction—specifically, the victim must be logged into their Sickbeard instance and visit a malicious page controlled by the attacker. However, once these conditions are met, the attack executes seamlessly without any additional user consent.

Root Cause

The root cause is CWE-352: Cross-Site Request Forgery. The Sickbeard application does not implement CSRF protection tokens on sensitive configuration endpoints that handle authentication settings. Without these tokens, the server cannot distinguish between legitimate user-initiated requests and forged requests originating from malicious third-party sites.

Attack Vector

The attack vector is network-based and requires user interaction. An attacker must craft a malicious HTML form or page that targets the Sickbeard configuration endpoint responsible for authentication settings. The form automatically submits when loaded, sending empty values for the web_username and web_password parameters to the vulnerable endpoint.

The attack flow is as follows: The attacker hosts a malicious page containing an auto-submitting form. The victim, who is logged into their Sickbeard instance, visits this page (typically through phishing or social engineering). The form submits to the Sickbeard configuration endpoint, clearing the authentication credentials. The victim's Sickbeard instance is now accessible without authentication.

For detailed technical information about the exploitation technique, refer to the Exploit-DB #48712 entry and the VulnCheck CSRF Advisory.

Detection Methods for CVE-2020-37026

Indicators of Compromise

• Unexpected changes to Sickbeard authentication settings with web_username or web_password cleared
• Web server logs showing POST requests to configuration endpoints from external referrers
• Authentication settings modified while the administrator was not actively configuring the application

Detection Strategies

• Monitor Sickbeard configuration files for unauthorized changes to authentication settings
• Review web server access logs for requests to /config/general/saveGeneral or similar configuration endpoints with suspicious referrer headers
• Implement network monitoring to detect cross-origin requests targeting internal Sickbeard instances

Monitoring Recommendations

• Configure alerting on any modifications to Sickbeard authentication configuration
• Deploy web application firewall (WAF) rules to detect and block CSRF attempts targeting known vulnerable endpoints
• Enable verbose logging on the Sickbeard instance to capture all configuration changes with timestamps and source information

How to Mitigate CVE-2020-37026

Immediate Actions Required

• Restrict network access to Sickbeard instances to trusted IP addresses only
• Place Sickbeard behind a reverse proxy with additional authentication layers
• Avoid browsing untrusted websites while logged into the Sickbeard admin interface
• Consider migrating to actively maintained alternatives such as Medusa or SickChill

Patch Information

No official patch is available for this vulnerability. The Sickbeard project appears to be unmaintained, with the archived website indicating the project is no longer actively developed. Users are strongly encouraged to migrate to maintained fork projects that have addressed CSRF vulnerabilities.

Workarounds

• Deploy Sickbeard behind a VPN to limit access to trusted users only
• Implement IP-based access controls at the firewall or web server level
• Use browser extensions that isolate sessions to prevent CSRF attacks from untrusted sites
• Configure your reverse proxy to add CSRF protection headers for all configuration endpoints

# Example nginx configuration to restrict access
location / {
    # Allow only trusted networks
    allow 192.168.1.0/24;
    allow 10.0.0.0/8;
    deny all;
    
    proxy_pass http://localhost:8081;
    proxy_set_header Host $host;
    proxy_set_header X-Real-IP $remote_addr;
}