Firepower Threat Defense
CVE-2020-3565
MEDIUM
Severity by source
AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N
Primary rating from NVD · only source for this CVE.
CVSS VectorNVD
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N
Lifecycle Timeline
1DescriptionNVD
A vulnerability in the TCP Intercept functionality of Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to bypass configured Access Control Policies (including Geolocation) and Service Polices on an affected system. The vulnerability exists because TCP Intercept is invoked when the embryonic connection limit is reached, which can cause the underlying detection engine to process the packet incorrectly. An attacker could exploit this vulnerability by sending a crafted stream of traffic that matches a policy on which TCP Intercept is configured. A successful exploit could allow the attacker to match on an incorrect policy, which could allow the traffic to be forwarded when it should be dropped. In addition, the traffic could incorrectly be dropped.
AnalysisAI
A vulnerability in the TCP Intercept functionality of Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to bypass configured Access Control Policies. Rated medium severity (CVSS 5.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. No vendor patch available.
Technical ContextAI
This vulnerability is classified under CWE-284. A vulnerability in the TCP Intercept functionality of Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to bypass configured Access Control Policies (including Geolocation) and Service Polices on an affected system. The vulnerability exists because TCP Intercept is invoked when the embryonic connection limit is reached, which can cause the underlying detection engine to process the packet incorrectly. An attacker could exploit this vulnerability by sending a crafted stream of traffic that matches a policy on which TCP Intercept is configured. A successful exploit could allow the attacker to match on an incorrect policy, which could allow the traffic to be forwarded when it should be dropped. In addition, the traffic could incorrectly be dropped. Affected products include: Cisco Firepower Threat Defense.
RemediationAI
No vendor patch is available at time of analysis. Monitor vendor advisories for updates. Apply vendor patches when available. Implement network segmentation and monitoring as interim mitigations.
More in Firepower Threat Defense
View allUpdate: On November 5, 2025, Cisco became aware of a new attack variant against devices running Cisco Secure ASA Softwar
A vulnerability in the Secure Sockets Layer (SSL) VPN functionality of the Cisco Adaptive Security Appliance (ASA) Softw
A vulnerability in the web services interface of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Th
A vulnerability in the web services interface for remote access VPN features of Cisco Adaptive Security Appliance (ASA)
A vulnerability in the web services interface of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Th
A vulnerability in the web interface of the Cisco Adaptive Security Appliance (ASA) could allow an unauthenticated, remo
Multiple vulnerabilities in the web services interface of Cisco Adaptive Security Appliance (ASA) Software and Cisco Fir
A vulnerability in the remote access VPN feature of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower
Multiple vulnerabilities in the multi-instance feature of Cisco Firepower Threat Defense (FTD) Software could allow an a
A vulnerability in the Remote Access VPN feature of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower
A vulnerability in the TLS cryptography functionality of Cisco Adaptive Security Appliance (ASA) Software and Cisco Fire
A vulnerability in the SSL VPN feature for Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat D
Same weakness CWE-284 – Improper Access Control
View allSame technique Authentication Bypass
View allShare
External POC / Exploit Code
Leaving vuln.today