CVE-2021-41551 in Connection Broker
Summary
by MITRE • 01/18/2022
Leostream Connection Broker 9.0.40.17 allows administrators to conduct directory traversal attacks by uploading z ZIP file that contains a symbolic link.
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Analysis
by VulDB Data Team • 01/20/2022
The vulnerability identified as CVE-2021-41551 affects the Leostream Connection Broker version 9.0.40.17, presenting a critical directory traversal risk that can be exploited by administrators with upload privileges. This flaw resides in the software's handling of ZIP file uploads, specifically when these archives contain symbolic links that can be manipulated to access restricted directories. The vulnerability stems from inadequate input validation and path resolution mechanisms within the file extraction process, allowing maliciously crafted ZIP archives to bypass normal security boundaries and potentially access sensitive system resources.
The technical implementation of this vulnerability involves the exploitation of symbolic link handling during ZIP file extraction operations. When an administrator uploads a ZIP file containing symbolic links, the Connection Broker fails to properly validate or sanitize these links before processing them. This creates a condition where symbolic links can point to arbitrary locations on the filesystem outside the intended upload directory. The flaw can be leveraged to traverse directories and potentially access configuration files, credentials, or other sensitive data that should remain protected from unauthorized access. This represents a classic directory traversal vulnerability that falls under the CWE-22 category, specifically involving improper limitation of a pathname to a restricted directory.
The operational impact of this vulnerability is significant for organizations relying on Leostream Connection Broker for remote desktop management and virtual desktop infrastructure. Attackers with administrative access or those able to escalate privileges can exploit this weakness to gain unauthorized access to system files, potentially leading to complete system compromise. The vulnerability enables attackers to read files outside the intended scope of the application, which could include sensitive configuration data, user credentials, or system logs. This risk is particularly concerning in enterprise environments where connection brokers serve as critical infrastructure components for remote access management and desktop virtualization solutions.
Organizations should immediately implement mitigations including restricting administrative privileges for ZIP file uploads, implementing strict input validation for all file types, and deploying network segmentation to limit access to affected systems. The implementation of proper path validation and symbolic link handling should be enforced through code-level fixes that prevent traversal attacks. Additionally, organizations should consider implementing file integrity monitoring solutions and regular security assessments to detect potential exploitation attempts. This vulnerability aligns with ATT&CK technique T1078 for Valid Accounts and T1566 for Phishing, as it may be leveraged after initial compromise to escalate privileges and maintain access to critical infrastructure components. Regular patching and vulnerability management programs should be enhanced to prevent similar issues in other software components that may be susceptible to similar directory traversal attacks.