CVE-2021-34754 in Firepower Threat Defense
Summary
by MITRE • 10/27/2021
Multiple vulnerabilities in the payload inspection for Ethernet Industrial Protocol (ENIP) traffic for Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to bypass configured rules for ENIP traffic. These vulnerabilities are due to incomplete processing during deep packet inspection for ENIP packets. An attacker could exploit these vulnerabilities by sending a crafted ENIP packet to the targeted interface. A successful exploit could allow the attacker to bypass configured access control and intrusion policies that should be activated for the ENIP packet.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 11/01/2021
The vulnerability identified as CVE-2021-34754 represents a critical flaw in Cisco Firepower Threat Defense software's Ethernet Industrial Protocol payload inspection capabilities. This weakness specifically affects the deep packet inspection mechanisms designed to analyze and filter industrial network traffic, particularly targeting ENIP communications that are fundamental to industrial control systems and automation environments. The vulnerability exists within the software's processing logic for handling Ethernet Industrial Protocol packets, which are commonly used in manufacturing and industrial environments for communication between programmable logic controllers and other industrial devices.
The technical root cause of this vulnerability stems from incomplete packet processing during the deep inspection phase of ENIP traffic analysis. When FTD software encounters ENIP packets, it fails to properly validate or process certain packet attributes, creating a pathway for malformed or crafted packets to bypass the intended security controls. This incomplete processing occurs during the payload inspection phase where the system should be thoroughly examining packet structure, headers, and content to enforce configured security policies. The flaw essentially allows attackers to craft packets that appear legitimate to the inspection engine but contain malicious elements that circumvent access control mechanisms. This represents a classic case of insufficient input validation and incomplete protocol parsing, which falls under CWE-20 - Improper Input Validation and CWE-444 - Incomplete Model.
From an operational perspective, this vulnerability poses significant risks to industrial environments that rely on Cisco Firepower appliances for network security. The ability to bypass configured access control and intrusion policies for ENIP traffic means that attackers could potentially gain unauthorized access to industrial control systems without detection. This could result in unauthorized modifications to industrial processes, data exfiltration from critical infrastructure, or disruption of manufacturing operations. The remote exploitation capability eliminates the need for physical access to the network, making it particularly dangerous for industrial environments where network security boundaries may be less strictly enforced. The vulnerability aligns with ATT&CK technique T1071.001 - Application Layer Protocol: Web Protocols, as it involves protocol-level manipulation to evade security controls, and T1566 - Phishing, since attackers might craft malicious ENIP packets to bypass network defenses.
Organizations should implement immediate mitigations including applying the latest security patches from Cisco, which address the incomplete packet processing logic and improve the validation of ENIP payload contents. Network segmentation strategies should be enhanced to isolate industrial networks from general corporate networks, reducing the attack surface for such exploits. Additionally, implementing additional monitoring and anomaly detection for ENIP traffic patterns can help identify potential exploitation attempts. Security teams should also review and update their industrial control system security policies to account for potential bypass scenarios, ensuring that multiple layers of defense are maintained even if one control mechanism is compromised. The vulnerability demonstrates the importance of proper protocol handling in network security appliances and highlights the need for comprehensive testing of industrial protocol support in security solutions.