CVE-2019-1981 in Firepower Threat Defense Software
Summary
by MITRE
A vulnerability in the normalization functionality of Cisco Firepower Threat Defense Software, Cisco FirePOWER Services Software for ASA, and Cisco Firepower Management Center Software could allow an unauthenticated, remote attacker to bypass filtering protections. The vulnerability is due to insufficient normalization of a text-based payload. An attacker could exploit this vulnerability by sending traffic that contains specifically obfuscated payloads through an affected device. An exploit could allow the attacker to bypass filtering and deliver malicious payloads to protected systems that would otherwise be blocked.
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Analysis
by VulDB Data Team • 11/27/2024
The vulnerability identified as CVE-2019-1981 represents a critical weakness in Cisco's threat defense solutions that affects multiple software components including Firepower Threat Defense Software, FirePOWER Services Software for ASA, and Firepower Management Center Software. This security flaw resides within the text-based payload normalization functionality, which serves as a fundamental component in detecting and filtering malicious network traffic. The issue stems from inadequate handling of obfuscated payloads that could potentially bypass the system's filtering mechanisms entirely, creating a significant security gap in network protection. According to CWE-20, this vulnerability falls under the category of "Improper Input Validation" where the system fails to properly normalize and validate text-based inputs before processing them through security filters.
The technical exploitation of this vulnerability occurs when an unauthenticated remote attacker crafts specifically obfuscated payloads that exploit the insufficient normalization process. The flaw allows attackers to manipulate text-based content in such a way that the affected devices fail to properly identify and block malicious traffic patterns. This occurs because the normalization functionality does not adequately process or standardize the payload content before it reaches the filtering logic, enabling attackers to inject malicious code or commands that would normally be detected and blocked by the security system. The vulnerability essentially creates a bypass mechanism where crafted payloads can slip through security controls designed to prevent their delivery to protected systems. This type of attack aligns with ATT&CK technique T1071.004 for application layer protocol: DNS, where attackers use protocol manipulation to evade detection.
The operational impact of CVE-2019-1981 extends beyond simple bypass of network filtering, potentially allowing attackers to deliver malicious payloads that would otherwise be blocked by the security infrastructure. Organizations using affected Cisco Firepower products face significant risk of data exfiltration, malware deployment, and other malicious activities that could compromise their network security posture. The vulnerability's remote and unauthenticated nature means that attackers do not require valid credentials or physical access to exploit the flaw, making it particularly dangerous as it can be leveraged from anywhere on the internet. This weakness undermines the fundamental security assumptions of network defense systems, potentially allowing attackers to establish persistent access or conduct advanced persistent threat operations against vulnerable organizations. The affected systems include both hardware and software components, making the scope of potential impact broader than typical network security vulnerabilities.
Mitigation strategies for CVE-2019-1981 should prioritize immediate patching of affected systems with the latest Cisco security updates that address the normalization functionality flaw. Organizations should also implement network segmentation and monitoring to detect anomalous traffic patterns that might indicate exploitation attempts. Additional defensive measures include enhanced logging and alerting for suspicious payload characteristics, implementing network behavior analysis tools, and conducting thorough vulnerability assessments of all affected Cisco Firepower deployments. Security teams should also review and update their incident response procedures to account for potential exploitation of this vulnerability, ensuring they can quickly identify and respond to any successful bypass attempts. The mitigation approach aligns with the NIST Cybersecurity Framework's Protect function, specifically focusing on system security planning and vulnerability management to reduce the attack surface and improve overall security resilience.