CVE-2020-27601 in BigBlueButton
Summary
by MITRE • 09/29/2022
In BigBlueButton before 2.2.7, lockSettingsProps.disablePrivateChat does not apply to already opened chats. This occurs in bigbluebutton-html5/imports/ui/components/chat/service.js.
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Analysis
by VulDB Data Team • 09/29/2022
The vulnerability identified as CVE-2020-27601 affects BigBlueButton versions prior to 2.2.7 and represents a critical access control flaw that undermines the intended security posture of the platform. This issue specifically relates to the chat functionality within the bigbluebutton-html5 component, where the lockSettingsProps.disablePrivateChat configuration parameter fails to properly enforce restrictions on existing chat sessions. The vulnerability exists in the service.js file within the chat component, indicating a design flaw in how the system handles dynamic privilege enforcement during active sessions. This represents a failure in the principle of least privilege and demonstrates poor input validation and access control implementation.
The technical flaw manifests when users attempt to disable private chat functionality through the lockSettingsProps.disablePrivateChat parameter. While this setting correctly prevents new private chat sessions from being initiated, it does not retroactively apply to chats that were already established before the setting was enforced. This creates a scenario where authorized users can bypass intended restrictions, potentially exposing sensitive communications to unauthorized participants. The vulnerability operates at the application logic level where runtime permissions are not properly synchronized with configuration changes, creating a persistent security gap that can be exploited by malicious actors who gain access to the platform during active sessions.
The operational impact of this vulnerability extends beyond simple privacy concerns to encompass potential data leakage and unauthorized communication access within collaborative environments. In educational and corporate settings where BigBlueButton is deployed for online meetings, webinars, and training sessions, this flaw could allow participants to access private conversations that should have been restricted. The vulnerability particularly affects scenarios where administrators attempt to enforce strict privacy controls during sensitive discussions, as the system fails to maintain consistency between configuration settings and active session states. This inconsistency creates a window of opportunity for information disclosure attacks and violates fundamental security principles of maintaining secure communication channels.
Mitigation strategies for CVE-2020-27601 should prioritize immediate deployment of BigBlueButton version 2.2.7 or later, which contains the necessary fixes to address the improper handling of chat session restrictions. Organizations should also implement monitoring solutions to detect unauthorized access patterns in chat functionality and establish regular security audits of configuration settings. The vulnerability aligns with CWE-668, which describes "Exposure of Resource to Wrong Sphere," and maps to ATT&CK technique T1078.004 for valid accounts, as it allows unauthorized access through proper account usage but with unintended privilege escalation. Security teams should also consider implementing additional network-level controls and session management policies to prevent exploitation, while ensuring proper testing of configuration changes before deployment in production environments.