CVE-2021-33191 in NiFi MiNiFi C++
Summary
by MITRE • 08/24/2021
From Apache NiFi MiNiFi C++ version 0.5.0 the c2 protocol implements an "agent-update" command which was designed to patch the application binary. This "patching" command defaults to calling a trusted binary, but might be modified to an arbitrary value through a "c2-update" command. Said command is then executed using the same privileges as the application binary. This was addressed in version 0.10.0
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Analysis
by VulDB Data Team • 08/26/2021
The vulnerability identified as CVE-2021-33191 affects Apache NiFi MiNiFi C++ versions 0.5.0 through 0.9.0, representing a critical security flaw in the remote management protocol implementation. This issue stems from the insecure execution of update commands within the C2 protocol, which is designed to enable remote management and patching of the application binary. The vulnerability manifests in the agent-update command functionality that was intended to provide legitimate patching capabilities but can be exploited through malicious manipulation of the c2-update command. The flaw resides in the protocol's trust model where the system defaults to executing a trusted binary but fails to properly validate or sanitize user-supplied parameters that can override this default behavior. This represents a classic privilege escalation vulnerability where an attacker can manipulate the update mechanism to execute arbitrary code with the same privileges as the running application, effectively bypassing normal security boundaries.
The technical implementation of this vulnerability involves the insecure handling of command execution parameters within the C2 protocol's update mechanism. When the c2-update command is received, it can modify the target binary path that the agent-update command will execute, allowing an attacker to specify any arbitrary binary path instead of the intended trusted binary. This misconfiguration occurs because the system does not properly validate or restrict the values that can be passed to the update command execution process. The vulnerability is particularly dangerous because it operates at the privilege level of the running application, meaning that if the MiNiFi C++ process is running with elevated permissions, the attacker can leverage this to execute malicious code with those same elevated privileges. This flaw directly aligns with CWE-78 and CWE-74 standards related to command injection vulnerabilities and improper input validation.
The operational impact of this vulnerability is severe and multifaceted across enterprise security environments that utilize Apache NiFi MiNiFi C++ for data flow management and edge computing operations. An attacker who can compromise the C2 communication channel or gain access to the management interface can execute arbitrary code on the target system, potentially leading to complete system compromise, data exfiltration, or lateral movement within the network. The vulnerability affects systems where the MiNiFi C++ agent is deployed in production environments, particularly in industrial control systems, IoT deployments, or any scenario where remote management capabilities are enabled. The attack surface is expanded by the fact that this vulnerability exists in the update mechanism itself, meaning that even legitimate update operations could be exploited if proper input validation is not implemented. This vulnerability also violates the principle of least privilege as defined in cybersecurity frameworks, since the system allows command execution with elevated privileges without proper authorization checks.
Mitigation strategies for CVE-2021-33191 should focus on immediate version upgrades to 0.10.0 or later, which contains the necessary fixes for the insecure command execution. Organizations should implement network segmentation and access controls around the C2 communication channels to limit exposure and prevent unauthorized access to the management interface. Additional defensive measures include implementing strict input validation for all update commands, monitoring for suspicious update activities, and ensuring that the MiNiFi C++ process runs with minimal required privileges. The fix addresses the vulnerability by implementing proper parameter validation and sanitization for the c2-update command, preventing arbitrary binary paths from being executed through the agent-update mechanism. Security teams should also consider implementing network-based intrusion detection systems to monitor for anomalous update behaviors and establish proper audit trails for all management operations. This vulnerability demonstrates the importance of secure coding practices and proper input validation in remote management protocols, as outlined in the ATT&CK framework's techniques for privilege escalation and command execution. Organizations should conduct comprehensive security assessments of their MiNiFi C++ deployments and ensure that all remote management features are properly secured against manipulation and unauthorized access.