CVE-2020-5196 in FTP Server Enterprise Edition
Summary
by MITRE
Cerberus FTP Server Enterprise Edition prior to versions 11.0.3 and 10.0.18 allows an authenticated attacker to create files, display hidden files, list directories, and list files without the permission to zip and download (or unzip and upload) files. There are multiple ways to bypass certain permissions by utilizing the zip and unzip features. As a result, users without permission can see files, folders, and hidden files, and can create directories without permission.
If you want to get best quality of vulnerability data, you may have to visit VulDB.
Analysis
by VulDB Data Team • 03/20/2024
CVE-2020-5196 represents a significant authorization bypass vulnerability in Cerberus FTP Server Enterprise Edition that undermines the core security model of file access controls. This vulnerability affects versions prior to 11.0.3 and 10.0.18, where authenticated attackers can exploit the zip and unzip functionality to circumvent permission restrictions that should normally prevent them from accessing or manipulating specific files and directories. The flaw resides in the improper validation of user permissions during archive operations, allowing malicious actors to leverage legitimate zip/unzip features as attack vectors for privilege escalation. The vulnerability is categorized under CWE-284 Access Control Bypass, which specifically addresses scenarios where systems fail to properly enforce access restrictions, particularly when legitimate system functions are misused for unauthorized access.
The technical exploitation of this vulnerability occurs through the manipulation of zip and unzip commands within the FTP server's interface. Attackers can create zip archives containing files they normally wouldn't have access to, effectively bypassing the restriction that prevents them from downloading files directly. Similarly, when unzipping files, unauthorized users can potentially extract content from directories they shouldn't be able to access. This permission bypass extends beyond simple file access to include the ability to enumerate hidden files and directories, which violates fundamental security principles of information hiding and access control. The vulnerability enables attackers to create new directories without proper authorization, further expanding their ability to manipulate the file system structure.
From an operational impact perspective, this vulnerability creates a serious risk for organizations relying on Cerberus FTP Server for file sharing and collaboration. The ability to view hidden files exposes sensitive system information that should remain concealed, potentially revealing system configurations, user data, or other confidential information. Directory enumeration capabilities allow attackers to map the file system structure without proper authorization, providing them with intelligence for further attacks. The unauthorized directory creation capability enables attackers to establish persistent footholds or organize stolen data in ways that evade detection. This vulnerability directly violates the principle of least privilege and can lead to data exfiltration, system compromise, or regulatory compliance violations in environments with strict data protection requirements.
Organizations should immediately implement mitigations including upgrading to the patched versions 11.0.3 and 10.0.18, which address the permission validation flaws in the zip/unzip functionality. Network segmentation and firewall rules should be implemented to restrict access to the FTP server from untrusted networks, limiting the attack surface. Additionally, monitoring should be enhanced to detect unusual zip/unzip activities that might indicate exploitation attempts. The ATT&CK framework categorizes this vulnerability under T1078 Valid Accounts and T1566 Phishing, as attackers may use compromised credentials to exploit this vulnerability. Regular security audits should verify that user permissions are properly enforced and that the zip/unzip features function correctly without allowing unauthorized access. System administrators should also review and restrict the zip/unzip functionality for users who do not require these capabilities, implementing principle of least privilege controls to minimize potential impact.