CVE-2020-3563: Cisco Firepower Threat Defense Software TCP Flood Denial of Service Vulnerability

Severity: high (CVSS 8.6 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2020-10-21 · updated 2026-08-11
Weakness: CWE-400

Description

A vulnerability in the packet processing functionality of Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. The vulnerability is due to inefficient memory management. An attacker could exploit this vulnerability by sending a large number of TCP packets to a specific port on an affected device. A successful exploit could allow the attacker to exhaust system memory, which could cause the device to reload unexpectedly. No manual intervention is needed to recover the device after it has reloaded.

Affected products

Cisco Firepower Threat Defense Software: from 6.3.0 before 6.3.0.6; from 6.4.0 before 6.4.0.10; from 6.5.0 before 6.5.0.5 — fixed in 6.3.0.6, 6.4.0.10, 6.5.0.5

How to fix

Upgrade to a fixed version: Cisco Firepower Threat Defense Software 6.3.0.6, 6.4.0.10, 6.5.0.5. Check the vendor advisory for mitigations.

References

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