CVE-2020-3564: Cisco Adaptive Security Appliance Software and Firepower Threat Defense Software FTP Inspection Bypass Vulnerability

Severity: medium (CVSS 5.3 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.3% 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-284

Description

A vulnerability in the FTP inspection engine of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to bypass FTP inspection. The vulnerability is due to ineffective flow tracking of FTP traffic. An attacker could exploit this vulnerability by sending crafted FTP traffic through an affected device. A successful exploit could allow the attacker to bypass FTP inspection and successfully complete FTP connections.

Affected products

Cisco Adaptive Security Appliance: before 9.6 — fixed in 9.6
Cisco ASA Software: from 9.8.0 before 9.8.4.26; from 9.9.0 before 9.9.2.80; from 9.10.0 before 9.10.1.44; from 9.12.0 before 9.12.4.4; from 9.13.0 before 9.13.1.13; from 9.14.0 before 9.14.1.19 — fixed in 9.10.1.44, 9.12.4.4, 9.13.1.13, 9.14.1.19, 9.8.4.26, 9.9.2.80
Cisco Firepower Threat Defense Software: before 6.3.0.6; from 6.4.0 before 6.4.0.10; from 6.5.0 before 6.5.0.5; from 6.6.0 before 6.6.1 — fixed in 6.3.0.6, 6.4.0.10, 6.5.0.5, 6.6.1

How to fix

Upgrade to a fixed version: Cisco Adaptive Security Appliance 9.6; Cisco ASA Software 9.10.1.44, 9.12.4.4, 9.13.1.13, 9.14.1.19; Cisco Firepower Threat Defense Software 6.3.0.6, 6.4.0.10, 6.5.0.5, 6.6.1. Check the vendor advisory for mitigations.

References

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