CVE-2020-27602 in BigBlueButton
Summary
by MITRE • 09/29/2022
BigBlueButton before 2.2.7 does not have a protection mechanism for separator injection in meetingId, userId, and authToken.
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Analysis
by VulDB Data Team • 09/29/2022
The vulnerability identified as CVE-2020-27602 affects BigBlueButton versions prior to 2.2.7 and represents a critical security flaw related to insufficient input validation and sanitization mechanisms. This vulnerability specifically targets the meetingId, userId, and authToken parameters within the BigBlueButton application framework, which is widely used for hosting online meetings and webinars. The absence of proper protection mechanisms for separator injection attacks creates a significant risk for unauthorized access and privilege escalation within the system. The vulnerability stems from the application's failure to adequately validate and sanitize user-provided input parameters that are used to construct internal identifiers and authentication tokens. When attackers can inject separator characters into these parameters, they can manipulate the internal data structures and potentially bypass authentication mechanisms or gain unauthorized access to meetings and user sessions.
The technical flaw manifests through the exploitation of insufficient input validation routines that should prevent malicious characters from being processed within critical system parameters. This weakness allows attackers to craft specially formatted meetingId, userId, or authToken values that contain separator characters such as semicolons, colons, or other delimiter characters that the system uses internally to separate different components of data structures. According to CWE classification, this vulnerability maps to CWE-77: "Improper Neutralization of Special Elements used in a Command ('Command Injection') and CWE-20: "Improper Input Validation," with potential implications for CWE-89: "Improper Neutralization of Special Elements used in an SQL Command ('SQL Injection') when the system interfaces with database components. The vulnerability can be leveraged to manipulate internal data processing flows and potentially cause unauthorized access to meeting sessions, user accounts, or system resources.
The operational impact of this vulnerability extends beyond simple authentication bypass scenarios and can result in serious consequences for organizations relying on BigBlueButton for educational or corporate meetings. Attackers could exploit this weakness to access private meeting sessions, manipulate user permissions, or gain elevated privileges within the system. The vulnerability affects the core authentication and session management mechanisms that are fundamental to the security posture of the BigBlueButton platform. Organizations using affected versions may experience unauthorized access to sensitive meeting data, potential data breaches, and disruption of legitimate services. The attack surface is particularly concerning because it affects parameters that are commonly used in API calls and session management, making the exploitation relatively straightforward for attackers with basic knowledge of the system architecture. This vulnerability can be classified under ATT&CK technique T1078.004: "Valid Accounts: Cloud Accounts" when attackers use manipulated session identifiers to gain access to user accounts, or T1566.001: "Phishing: Spearphishing Attachment" when attackers craft malicious sessions that appear legitimate to users.
Mitigation strategies for CVE-2020-27602 primarily involve upgrading to BigBlueButton version 2.2.7 or later, which includes proper input sanitization and validation mechanisms for the affected parameters. Organizations should also implement additional security controls such as input filtering at the network level, monitoring for unusual parameter patterns, and regular security audits of API endpoints. The implementation of proper parameter validation should include the use of allowlists for valid characters, proper encoding of special characters, and regular input sanitization routines that prevent separator injection attacks. Security teams should also consider implementing rate limiting and anomaly detection mechanisms to identify potential exploitation attempts. Additional protective measures include regular security training for administrators, implementing proper access controls, and maintaining up-to-date security monitoring systems that can detect unusual parameter usage patterns. Organizations should also review their network configurations to ensure that API endpoints are properly secured and that unnecessary exposure is minimized. The vulnerability highlights the importance of input validation in web applications and demonstrates how seemingly simple parameter handling can create significant security risks when proper sanitization mechanisms are not implemented.