CVE-2022-29169 is a vulnerability in BigBlueButton, an open-source web conferencing system widely used for online meetings and virtual classrooms. The issue arises from improper input validation (CWE-20) in the useragent library component, specifically in the function lookupUserAgent(), which parses the User-Agent HTTP header using regular expressions. Versions of BigBlueButton starting from 2.2 up to but not including 2.3.19, 2.4.0 up to but not including 2.4.7, and 2.5-alpha-1 up to but not including 2.5.0-beta.2 are affected. An attacker can craft a malicious User-Agent string containing a carefully designed regular expression payload (notably involving the term 'SmartWatch') that triggers a Regular Expression Denial of Service (ReDoS) attack. This causes excessive CPU consumption in the bbb-html5 service, leading to denial of service conditions where legitimate users may be unable to access or use the conferencing system effectively. The vulnerability stems from the useragent library’s regex-based parsing, which is susceptible to catastrophic backtracking when processing malicious input. The BigBlueButton maintainers addressed this by removing the vulnerable htmlclient/useragent component in versions 2.3.19, 2.4.7, and 2.5.0-beta.2. As an interim mitigation, disabling NginX forwarding requests to the vulnerable handler is recommended. There are no known exploits in the wild reported to date, but the nature of the vulnerability allows unauthenticated attackers to cause service disruption remotely by sending crafted HTTP requests. This vulnerability impacts the availability of BigBlueButton services but does not directly compromise confidentiality or integrity.

For European organizations relying on BigBlueButton for remote collaboration, education, or conferencing, this vulnerability poses a risk of service disruption through denial of service attacks. Given the increased reliance on virtual communication platforms, especially in education and public sector institutions, exploitation could lead to significant operational downtime, impacting productivity and service delivery. The vulnerability affects the availability of the conferencing service, potentially interrupting critical meetings, online classes, or public services. Since exploitation requires only sending a malicious User-Agent header, it can be triggered remotely without authentication, increasing the attack surface. While there is no direct data breach risk, the denial of service could indirectly affect business continuity and user trust. Organizations with high usage of BigBlueButton, particularly in sectors like education, government, and public administration, may experience reputational damage and operational delays if targeted. The absence of known exploits suggests limited current threat activity, but the ease of exploitation and the widespread use of BigBlueButton in Europe warrant proactive mitigation.

1. Upgrade affected BigBlueButton instances to versions 2.3.19, 2.4.7, or 2.5.0-beta.2 or later, where the vulnerable useragent component has been removed. 2. If immediate upgrade is not feasible, implement the recommended workaround by disabling NginX forwarding of requests to the vulnerable bbb-html5 service handler, as detailed in the official GitHub Security Advisory. 3. Implement Web Application Firewall (WAF) rules to detect and block suspicious User-Agent headers containing patterns indicative of ReDoS payloads, especially those involving 'SmartWatch' or other anomalous regex patterns. 4. Monitor logs for unusual spikes in CPU usage or repeated requests with malformed User-Agent headers to detect potential exploitation attempts early. 5. Limit exposure of the BigBlueButton service to trusted networks or VPNs where possible to reduce attack surface. 6. Conduct regular security assessments and penetration testing focused on input validation and denial of service vectors in web-facing services. 7. Educate administrators on the importance of timely patching and monitoring for this specific vulnerability given its potential to disrupt service availability.