BigBlueButton version before 2.2.7 had a security vulnerability that allowed remote authenticated users to read local files and perform Server-Side Request Forgery (SSRF) attacks. This vulnerability could be exploited by uploading an Office document containing a malicious URL in an ODF xlink field, which could then be used to access local files and perform unauthorized actions on the server.

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About BigBlueButton

BigBlueButton is an open-source web conferencing platform designed specifically for online learning. It offers a wide range of features including real-time sharing of audio, video, slides, chat, and screen, along with the ability to record sessions for later playback. This platform is highly customizable and can be integrated with major learning management systems, supporting educators and students in virtual classrooms and remote learning environments. With a strong focus on user accessibility and ease of use, BigBlueButton provides an effective and efficient solution for digital education.

Mitigation

1. Update BigBlueButton to version 2.2.7 or later, as the vulnerability is addressed in this release.
2. Regularly apply security patches and updates to ensure all software components are up-to-date.
3. Limit file upload permissions to trusted users only, reducing the risk of a malicious file being uploaded.
4. Implement input validation and sanitization measures to check for and remove potentially malicious content from uploaded files.
5. Deploy a web application firewall (WAF) to monitor and filter incoming traffic and block any attempts to exploit vulnerabilities.
6. Educate users about the risks of uploading files from untrusted sources and encourage safe practices.
7. Monitor server logs for any unusual activity that could indicate an attempted attack or successful exploitation

Exploit Scenario

The exploit scenario for BigBlueButton before version 2.2.7 involves a remote authenticated user leveraging a vulnerability to both read local files and conduct Server-Side Request Forgery (SSRF) attacks. This is achieved by uploading an Office document containing a specially crafted URL within an Open Document Format (ODF) xlink field. By doing so, the attacker can manipulate the application to access unauthorized files or interact with internal systems that should not be exposed externally.

DockerHub Link

To try out a demo environment for CVE-2020-25820, you can visit our DockerHub repository here

Video Tutorial

Video tutorials for exploiting CVE-2020-25820 is available here

About OpenExploit

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