CVE-2020-11997 in Guacamole
Summary
by MITRE • 01/20/2021
Apache Guacamole 1.2.0 and earlier do not consistently restrict access to connection history based on user visibility. If multiple users share access to the same connection, those users may be able to see which other users have accessed that connection, as well as the IP addresses from which that connection was accessed, even if those users do not otherwise have permission to see other users.
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Analysis
by VulDB Data Team • 02/15/2021
Apache Guacamole represents a widely adopted web-based remote desktop gateway that enables secure access to remote desktop environments through a browser interface. The vulnerability identified as CVE-2020-11997 exposes a critical flaw in the application's access control mechanisms specifically concerning connection history data. This issue affects all versions prior to 1.2.1 and fundamentally undermines the principle of least privilege by creating inconsistent access restrictions. The flaw manifests when multiple users share access to identical connections, allowing unauthorized information disclosure through the connection history subsystem.
The technical root cause of this vulnerability stems from inadequate authorization checks within the connection history retrieval logic. When users access shared connections, the system fails to properly validate whether each user should have visibility into the complete history of that connection. This weakness creates a data exposure scenario where users can inadvertently discover information about other users' activities, including temporal access patterns and network location details. The vulnerability operates at the application layer and directly impacts the confidentiality aspect of the CIA triad, as it permits unauthorized data access through legitimate application interfaces. This issue maps to CWE-284 Access Control Bypass, specifically addressing insufficient access control validation in multi-user environments where shared resources are involved.
The operational impact of CVE-2020-11997 extends beyond simple information disclosure to potentially enable more sophisticated attack vectors. An attacker who gains access to a shared connection could use this vulnerability to perform reconnaissance activities by identifying other users who have accessed specific connections, potentially mapping user behavior patterns and network access points. The exposure of IP addresses from which connections were accessed creates additional attack surface information that could be leveraged for further exploitation. This vulnerability particularly affects organizations that rely on shared connection resources, as it undermines the trust model that should exist between users and their assigned access permissions. The flaw also violates fundamental security principles established in the NIST Cybersecurity Framework, specifically addressing the protection of information assets through appropriate access controls.
Organizations utilizing Apache Guacamole versions prior to 1.2.1 should implement immediate mitigation strategies to address this vulnerability. The primary recommended action involves upgrading to Apache Guacamole version 1.2.1 or later, which includes the necessary access control fixes. Additionally, administrators should review existing user permissions and connection sharing configurations to minimize the exposure surface. Network segmentation and monitoring controls should be enhanced to detect unusual access patterns that might indicate exploitation attempts. The vulnerability demonstrates the importance of proper access control implementation in multi-tenant environments and aligns with ATT&CK technique T1078 Valid Accounts, as it exploits legitimate user access to gain unauthorized information disclosure. Organizations should also consider implementing additional logging and monitoring of connection history access events to detect potential abuse of this vulnerability.