CVE-2018-6439 in Fabric OS
Summary
by MITRE
A Vulnerability in the configdownload command of Brocade Fabric OS command line interface (CLI) versions before 8.2.1, 8.1.2f, 8.0.2f, 7.4.2d could allow a local attacker to escape the restricted shell and, gain root access.
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Analysis
by VulDB Data Team • 06/03/2026
The vulnerability identified as CVE-2018-6439 resides within the Brocade Fabric OS command line interface where the configdownload command fails to properly validate input parameters. This flaw affects multiple versions including those before 8.2.1, 8.1.2f, 8.0.2f, and 7.4.2d, creating a significant security risk for network infrastructure administrators who rely on these systems. The issue stems from inadequate sanitization of command line arguments that are processed by the restricted shell environment, allowing malicious input to bypass intended security boundaries.
The technical implementation of this vulnerability exploits a privilege escalation vector through improper input handling within the CLI subsystem. When the configdownload command processes user-supplied parameters, it fails to properly validate or sanitize the input before executing system-level operations. This misconfiguration enables a local attacker with access to the restricted shell environment to craft specific command sequences that can escape the constrained execution context. The vulnerability operates under CWE-78 principle of improper neutralization of special elements used in shell commands, where user-controllable data is directly passed to shell execution without proper sanitization.
From an operational perspective, this vulnerability represents a critical threat to network security infrastructure as it allows local attackers to escalate privileges from standard user level to root access. The restricted shell environment is designed to limit user capabilities and prevent direct system-level access, but this flaw undermines those security controls entirely. Network administrators who have not updated their Brocade Fabric OS installations to the patched versions face significant risk of unauthorized system compromise, potentially leading to complete network infrastructure control. The impact extends beyond simple privilege escalation as it can enable attackers to modify network configurations, access sensitive data, and potentially disrupt network operations.
The attack surface for this vulnerability is particularly concerning given that it requires only local access to the system, making it accessible to anyone with physical or network access to the device. This local privilege escalation vulnerability aligns with ATT&CK technique T1068 which covers 'Exploitation for Privilege Escalation' and specifically targets the exploitation of local system vulnerabilities. The threat model suggests that adversaries with low-privilege accounts or physical access could leverage this flaw to gain full administrative control over the fabric switch. Organizations should implement immediate remediation through patch management processes and consider additional security controls such as monitoring for unusual command execution patterns and implementing network segmentation to limit access to critical infrastructure devices.
Mitigation strategies should include immediate deployment of the vendor-provided security patches for all affected versions, along with comprehensive security assessments of the network infrastructure. System administrators should also consider implementing additional controls such as disabling unnecessary services, restricting local access to administrative accounts, and establishing robust monitoring procedures for suspicious command execution patterns. The vulnerability demonstrates the critical importance of input validation in privileged execution contexts and serves as a reminder of the need for comprehensive security testing of command line interfaces in network infrastructure devices.