CVE-2018-16494 in VOS
Summary
by MITRE • 05/26/2021
In VOS and overly permissive "umask" may allow for authorized users of the server to gain unauthorized access through insecure file permissions that can result in an arbitrary read, write, or execution of newly created files and directories. Insecure umask setting was present throughout the Versa servers.
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Analysis
by VulDB Data Team • 05/30/2021
CVE-2018-16494 represents a critical privilege escalation vulnerability affecting Versa Networks servers where overly permissive umask settings create persistent security weaknesses across the entire server infrastructure. This vulnerability stems from the improper configuration of umask values during file and directory creation processes, which directly violates fundamental security principles outlined in the Common Weakness Enumeration framework under CWE-276. The flaw allows authorized users to manipulate file permissions in ways that can lead to arbitrary read, write, and execution access to newly created system resources, effectively undermining the principle of least privilege that is central to secure system design.
The technical implementation of this vulnerability occurs when the umask value is set to an overly permissive state such as 000 or 007, which results in newly created files and directories inheriting world-readable, world-writable, or world-executable permissions. This configuration creates a persistent backdoor mechanism where legitimate users can exploit the system's default permission settings to gain unauthorized access to sensitive data and system resources. The vulnerability is particularly dangerous because it affects the entire Versa server ecosystem, meaning that any authorized user with access to the system can potentially escalate their privileges and compromise other users' data or system integrity.
The operational impact of this vulnerability extends beyond simple privilege escalation to encompass a wide range of potential security breaches including data exfiltration, system compromise, and unauthorized code execution. Attackers can leverage this weakness to create malicious files with elevated permissions, establish persistent backdoors, or access sensitive configuration files that contain authentication credentials or system secrets. This vulnerability directly maps to several techniques described in the MITRE ATT&CK framework, particularly those related to privilege escalation through weak permissions and persistence mechanisms. The widespread nature of the issue across all Versa servers means that organizations cannot simply patch individual components but must address the root cause at the system configuration level.
Organizations affected by this vulnerability should immediately implement comprehensive remediation measures including setting proper umask values to restrict file permissions to the minimum necessary for system operation, typically 022 or 077 depending on specific requirements. System administrators must conduct thorough audits of all server configurations to identify and correct insecure umask settings, while implementing monitoring solutions to detect unauthorized permission changes. The vulnerability also highlights the importance of regular security configuration reviews and adherence to security baseline standards such as those defined in the Center for Internet Security (CIS) benchmarks, which specifically recommend restrictive umask settings to prevent exactly this type of security weakness. Additionally, implementing automated configuration management tools can help maintain consistent security posture across all system components and prevent regression of these insecure settings.