CVE-2022-29169
📋 TL;DR
BigBlueButton web conferencing systems are vulnerable to regular expression denial of service (ReDoS) attacks through malicious User-Agent headers. Attackers can send specially crafted requests containing 'SmartWatch' patterns that cause excessive CPU consumption, potentially crashing the bbb-html5 service. This affects all BigBlueButton deployments running vulnerable versions.
💻 Affected Systems
- BigBlueButton
📦 What is this software?
Bigbluebutton by Bigbluebutton
Bigbluebutton by Bigbluebutton
Bigbluebutton by Bigbluebutton
Bigbluebutton by Bigbluebutton
Bigbluebutton by Bigbluebutton
Bigbluebutton by Bigbluebutton
Bigbluebutton by Bigbluebutton
Bigbluebutton by Bigbluebutton
Bigbluebutton by Bigbluebutton
⚠️ Risk & Real-World Impact
Worst Case
Complete denial of service for the BigBlueButton instance, making web conferencing services unavailable to all users until service restart.
Likely Case
Degraded performance or temporary service disruption affecting user experience during meetings.
If Mitigated
Minimal impact with proper rate limiting, request filtering, or patched versions preventing the regex processing issue.
🎯 Exploit Status
Exploitation requires only HTTP requests with malicious User-Agent headers. No authentication or special privileges needed.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 2.3.19, 2.4.7, or 2.5.0-beta.2
Vendor Advisory: https://github.com/bigbluebutton/bigbluebutton/security/advisories/GHSA-rwrv-p665-4vwp
Restart Required: Yes
Instructions:
1. Backup your BigBlueButton configuration and data. 2. Update to version 2.3.19, 2.4.7, or 2.5.0-beta.2 using your package manager. 3. Restart all BigBlueButton services. 4. Verify the update was successful.
🔧 Temporary Workarounds
Disable Nginx forwarding to vulnerable handler
linuxConfigure Nginx to not forward requests to the vulnerable useragent handler as described in the GitHub advisory
# Modify Nginx configuration to exclude useragent processing
# Specific configuration changes depend on your deployment
🧯 If You Can't Patch
- Implement web application firewall (WAF) rules to block or sanitize User-Agent headers containing suspicious patterns
- Apply rate limiting to requests with unusual User-Agent strings to prevent DoS conditions
🔍 How to Verify
Check if Vulnerable:
Check BigBlueButton version: if between 2.2-2.3.18, 2.4.0-2.4.6, or exactly 2.5.0-beta.1, you are vulnerableCheck Version:
bbb-conf --check | grep 'BigBlueButton'Verify Fix Applied:
Verify version is 2.3.19, 2.4.7, or 2.5.0-beta.2 or higher, and test with normal User-Agent requests📡 Detection & Monitoring
Log Indicators:
- High CPU usage on bbb-html5 service
- Multiple requests with unusual User-Agent strings containing 'SmartWatch' patterns
- Service restart logs
Network Indicators:
- HTTP requests with malformed User-Agent headers
- Unusual traffic patterns to BigBlueButton endpoints
SIEM Query:
source="nginx" AND (user_agent="*SmartWatch*" OR user_agent MATCHES "*[regex patterns]*")🔗 References
- https://github.com/bigbluebutton/bigbluebutton/pull/14886
- https://github.com/bigbluebutton/bigbluebutton/pull/14896
- https://github.com/bigbluebutton/bigbluebutton/security/advisories/GHSA-rwrv-p665-4vwp
- https://github.com/bigbluebutton/bigbluebutton/pull/14886
- https://github.com/bigbluebutton/bigbluebutton/pull/14896
- https://github.com/bigbluebutton/bigbluebutton/security/advisories/GHSA-rwrv-p665-4vwp
