CVE-2020-36892: CRITICAL Severity Vulnerability | Secably CVE Database

Summary

CVE-2020-36892 is a critical unauthenticated privilege escalation vulnerability affecting Eibiz i-Media Server Digital Signage 3.8.0. An attacker can exploit the updateUser object via the /messagebroker/amf endpoint to modify user roles, potentially gaining administrative access without authentication.

Technical Details

This vulnerability stems from a lack of authentication checks when handling requests to the updateUser object within the Eibiz i-Media Server Digital Signage 3.8.0 application. The application utilizes the Action Message Format (AMF) protocol for communication, specifically through the /messagebroker/amf endpoint. An attacker can craft a malicious AMF request targeting the updateUser object to modify the roles associated with existing user accounts. By manipulating the role settings, an attacker can elevate their privileges to that of an administrator, effectively taking control of the application. The vulnerability exists because the application does not properly validate the identity of the user making the updateUser request, allowing unauthenticated users to perform privileged actions.

The AMF protocol's binary nature can make exploitation less obvious, but readily available tools and libraries can be used to construct and send the malicious requests. The lack of authentication on this critical function makes exploitation straightforward.

Affected Products and Versions

Eibiz i-Media Server Digital Signage 3.8.0

Impact Assessment

Successful exploitation of CVE-2020-36892 can have severe consequences. An attacker gaining administrative privileges can:

Completely compromise the digital signage system.
Modify or inject content displayed on screens, potentially spreading misinformation or malicious content.
Access sensitive data stored within the system, including user credentials and configuration information.
Disrupt the normal operation of the digital signage network, causing service outages.
Use the compromised system as a launchpad for further attacks on the internal network.

Remediation

Immediate Actions

Isolate the affected system: Disconnect the Eibiz i-Media Server Digital Signage 3.8.0 instance from the network to prevent further exploitation.
Monitor network traffic: Analyze network traffic for suspicious activity targeting the /messagebroker/amf endpoint.
Review user accounts: Check for any unauthorized changes to user roles or the creation of new administrative accounts.

Long-term Solutions

Apply the vendor-supplied patch: Contact Eibiz for a security patch that addresses the unauthenticated privilege escalation vulnerability. If a patch is unavailable, consider migrating to a different digital signage solution.
Implement strong authentication: Enforce strong authentication mechanisms for all administrative functions, including the updateUser object.
Restrict access to the AMF endpoint: Limit access to the /messagebroker/amf endpoint to authorized users only.
Regular Security Audits: Conduct regular security audits and penetration testing to identify and address vulnerabilities proactively.

References

Detection & Scanning

Detecting CVE-2020-36892 involves analyzing network traffic for suspicious AMF requests targeting the /messagebroker/amf endpoint. Specifically, look for requests to the updateUser object that attempt to modify user roles without proper authentication. Network intrusion detection systems (IDS) and security information and event management (SIEM) solutions can be configured to alert on such activity. Vulnerability scanners can also be used to identify instances of Eibiz i-Media Server Digital Signage 3.8.0 that are potentially vulnerable.

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