CVE-2017-3883 in Firepower Extensible Operating System
Summary
by MITRE
A vulnerability in the authentication, authorization, and accounting (AAA) implementation of Cisco Firepower Extensible Operating System (FXOS) and NX-OS System Software could allow an unauthenticated, remote attacker to cause an affected device to reload. The vulnerability occurs because AAA processes prevent the NX-OS System Manager from receiving keepalive messages when an affected device receives a high rate of login attempts, such as in a brute-force login attack. System memory can run low on the FXOS devices under the same conditions, which could cause the AAA process to unexpectedly restart or cause the device to reload. An attacker could exploit this vulnerability by performing a brute-force login attack against a device that is configured with AAA security services. A successful exploit could allow the attacker to cause the affected device to reload. This vulnerability affects the following Cisco products if they are running Cisco FXOS or NX-OS System Software that is configured for AAA services: Firepower 4100 Series Next-Generation Firewall, Firepower 9300 Security Appliance, Multilayer Director Switches, Nexus 1000V Series Switches, Nexus 1100 Series Cloud Services Platforms, Nexus 2000 Series Switches, Nexus 3000 Series Switches, Nexus 3500 Platform Switches, Nexus 5000 Series Switches, Nexus 5500 Platform Switches, Nexus 5600 Platform Switches, Nexus 6000 Series Switches, Nexus 7000 Series Switches, Nexus 7700 Series Switches, Nexus 9000 Series Switches in NX-OS mode, Nexus 9500 R-Series Line Cards and Fabric Modules, Unified Computing System (UCS) 6100 Series Fabric Interconnects, UCS 6200 Series Fabric Interconnects, UCS 6300 Series Fabric Interconnects. Cisco Bug IDs: CSCuq58760, CSCuq71257, CSCur97432, CSCus05214, CSCux54898, CSCvc33141, CSCvd36971, CSCve03660.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 01/19/2021
The vulnerability described in CVE-2017-3883 represents a critical denial-of-service weakness within Cisco's authentication, authorization, and accounting infrastructure that affects multiple network device families. This flaw resides in the Firepower Extensible Operating System (FXOS) and NX-OS System Software implementations, specifically targeting the AAA processing mechanisms that govern device access control. The vulnerability manifests when devices experience high-rate login attempts, creating a condition where the NX-OS System Manager fails to receive critical keepalive messages, ultimately leading to system instability and potential device reloads. This issue demonstrates the fragility of authentication systems when subjected to brute-force attack patterns, where legitimate system processes become overwhelmed by malicious activity.
The technical exploitation of this vulnerability follows a well-defined pattern that aligns with common attack methodologies documented in the MITRE ATT&CK framework under the T1110 technique category for Brute Force. When an attacker initiates a sustained brute-force login attack against affected devices, the AAA subsystem becomes overwhelmed with authentication requests, causing a cascade of failures in the system's communication protocols. The underlying mechanism involves the disruption of keepalive message delivery between the NX-OS System Manager and AAA processes, creating a feedback loop that depletes available system memory resources. This memory exhaustion condition forces the AAA process to restart unexpectedly, which can ultimately result in complete device reload operations. The vulnerability specifically targets the interplay between authentication handling and system resource management, creating a scenario where security mechanisms become the source of system instability rather than protection.
The operational impact of this vulnerability extends across numerous Cisco product lines, affecting everything from next-generation firewalls to data center switches and fabric interconnects. Devices in the Firepower 4100 Series, Firepower 9300 Security Appliance, various Nexus switch series, and UCS fabric interconnects all face identical risk profiles when configured with AAA services. The widespread nature of this vulnerability means that organizations with diverse network infrastructures face coordinated risk exposure, as multiple device types within the same network environment can be simultaneously compromised by a single attack vector. Network administrators must consider the cascading effects of a successful exploit, as device reloads can disrupt network connectivity, potentially creating service outages that extend beyond the immediate affected device to impact entire network segments or data center operations.
Mitigation strategies for CVE-2017-3883 require a multi-layered approach that addresses both immediate protection and long-term system hardening. Organizations should implement rate limiting mechanisms at network boundaries to prevent excessive login attempts from reaching target devices, effectively creating a first line of defense against brute-force attacks. The implementation of intrusion prevention systems with signature-based detection capabilities can help identify and block malicious authentication attempts before they can exploit the vulnerability. Network segmentation and access control policies should be strengthened to limit the exposure of critical network devices to external threats. Additionally, organizations should consider implementing account lockout mechanisms and monitoring systems that can detect unusual authentication patterns that may indicate brute-force attack activity. The vulnerability's classification under CWE-284 (Improper Access Control) and its relationship to CWE-400 (Uncontrolled Resource Consumption) emphasizes the need for comprehensive resource management and access control policies. Regular system updates and patches should be prioritized, with particular attention to the specific bug IDs referenced in the vulnerability disclosure, as these represent the exact conditions that trigger the problematic behavior in the affected software versions.