CVE-2019-1978 in Firepower Threat Defense Software
Summary
by MITRE
A vulnerability in the stream reassembly component 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 improper reassembly of traffic streams. An attacker could exploit this vulnerability by sending crafted streams through an affected device. An exploit could allow the attacker to bypass filtering and deliver malicious requests to protected systems that would otherwise be blocked.
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Analysis
by VulDB Data Team • 06/14/2025
The vulnerability identified as CVE-2019-1978 represents a critical flaw in Cisco's network security infrastructure, specifically affecting Firepower Threat Defense Software, FirePOWER Services Software for ASA, and Firepower Management Center Software. This vulnerability resides within the stream reassembly component of these security solutions, which is responsible for processing and reconstructing network traffic streams for inspection and filtering. The flaw enables an unauthenticated remote attacker to circumvent the intended security controls, fundamentally undermining the protective capabilities of these devices. The vulnerability has been categorized under CWE-129, which deals with improper validation of input boundaries, and aligns with ATT&CK technique T1071.004 for application layer protocol manipulation, demonstrating how attackers can exploit network protocol handling weaknesses to bypass security controls.
The technical exploitation of CVE-2019-1978 occurs through the improper reassembly of network traffic streams, where the affected software fails to correctly handle fragmented network packets during the reconstruction process. When an attacker crafts specific stream patterns and transmits them through an affected device, the flawed stream reassembly logic allows malicious traffic to bypass the normal filtering mechanisms. This occurs because the software does not properly validate or handle edge cases in stream reconstruction, particularly when dealing with overlapping or irregularly fragmented packets. The vulnerability essentially creates a pathway for attackers to inject traffic that would normally be blocked by the security policies, enabling them to reach protected internal systems that should be shielded from external threats.
The operational impact of this vulnerability is severe and multifaceted, as it allows remote attackers to completely bypass network security controls without requiring authentication or specialized privileges. Organizations relying on affected Cisco Firepower devices face significant risk of unauthorized access to their internal networks, as the vulnerability enables attackers to deliver malicious requests directly to protected systems that would otherwise be blocked by the security infrastructure. This bypass capability can lead to data exfiltration, lateral movement within networks, and potential compromise of critical assets. The vulnerability's remote exploitability means that attackers can target these devices from outside the network perimeter, making it particularly dangerous for organizations with exposed firewalls or perimeter security devices.
Mitigation strategies for CVE-2019-1978 should prioritize immediate software updates from Cisco, specifically addressing the stream reassembly component vulnerabilities in Firepower Threat Defense Software, FirePOWER Services Software for ASA, and Firepower Management Center Software. Organizations should implement network segmentation to limit the potential impact of exploitation, deploy additional monitoring and detection capabilities to identify anomalous traffic patterns, and ensure that all affected devices are updated with the latest security patches. Network administrators should also consider implementing temporary network restrictions or disabling unnecessary services on affected devices until patches can be properly deployed. The vulnerability's classification under CWE-129 and its alignment with ATT&CK techniques for protocol manipulation emphasize the need for comprehensive security measures that address both the immediate patching requirements and broader network security posture improvements.