CVE-2020-12112
📋 TL;DR
CVE-2020-12112 is a local file inclusion vulnerability in BigBlueButton that allows remote attackers to read sensitive files on the server. This affects BigBlueButton installations before version 2.2.5. Attackers can potentially access configuration files, credentials, or other sensitive data.
💻 Affected Systems
- BigBlueButton
📦 What is this software?
Bigbluebutton by Bigbluebutton
⚠️ Risk & Real-World Impact
Worst Case
Full server compromise through credential theft from configuration files, followed by lateral movement within the network.
Likely Case
Sensitive file disclosure including configuration files, environment variables, and potentially user data.
If Mitigated
Limited impact with proper network segmentation and file system permissions restricting access to sensitive files.
🎯 Exploit Status
Exploit code is publicly available and requires minimal technical skill to execute.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 2.2.5
Vendor Advisory: https://github.com/bigbluebutton/bigbluebutton/releases/tag/v2.2.5
Restart Required: Yes
Instructions:
1. Backup your BigBlueButton installation. 2. Update to version 2.2.5 using the official upgrade instructions. 3. Restart all BigBlueButton services. 4. Verify the fix is applied.
🔧 Temporary Workarounds
Web Application Firewall (WAF) Rules
allImplement WAF rules to block path traversal attempts and local file inclusion patterns.
File System Permissions
linuxRestrict read permissions on sensitive directories and configuration files.
chmod 600 /var/lib/tomcat7/webapps/bigbluebutton/WEB-INF/classes/bigbluebutton.properties
chmod 700 /etc/bigbluebutton
🧯 If You Can't Patch
- Implement strict network segmentation to isolate BigBlueButton servers from sensitive systems.
- Deploy a web application firewall with rules specifically blocking path traversal patterns.
🔍 How to Verify
Check if Vulnerable:
Check if BigBlueButton version is below 2.2.5 by examining the installed version.Check Version:
bbb-conf --check | grep 'BigBlueButton'Verify Fix Applied:
Confirm version is 2.2.5 or higher and test that path traversal attempts are blocked.📡 Detection & Monitoring
Log Indicators:
- Unusual file access patterns in web server logs
- Path traversal strings in URL parameters
- Multiple failed attempts to access sensitive file paths
Network Indicators:
- HTTP requests containing '../' patterns
- Requests for known sensitive file paths like /etc/passwd or configuration files
SIEM Query:
source="web_server_logs" AND (url="*../*" OR url="*/etc/*" OR url="*/WEB-INF/*")🔗 References
- https://cwe.mitre.org/data/definitions/23.html
- https://github.com/bigbluebutton/bigbluebutton/compare/v2.2.4...v2.2.5
- https://github.com/tchenu/CVE-2020-12112
- https://twitter.com/bigbluebutton/status/1252706369486180353
- https://twitter.com/thibeault_chenu/status/1249976515917422593
- https://cwe.mitre.org/data/definitions/23.html
- https://github.com/bigbluebutton/bigbluebutton/compare/v2.2.4...v2.2.5
- https://github.com/tchenu/CVE-2020-12112
- https://twitter.com/bigbluebutton/status/1252706369486180353
- https://twitter.com/thibeault_chenu/status/1249976515917422593
