CVE-2019-12655: Cisco IOS

High severity, CVSS 7.5. EPSS: 2% chance of exploitation in the next 30 days.

A vulnerability in the FTP application layer gateway (ALG) functionality used by Network Address Translation (NAT), NAT IPv6 to IPv4 (NAT64), and the Zone-Based Policy Firewall (ZBFW) in Cisco IOS XE Software could allow an unauthenticated, remote attacker to cause an affected device to reload. The vulnerability is due to a buffer overflow that occurs when an affected device inspects certain FTP traffic. An attacker could exploit this vulnerability by performing a specific FTP transfer through the device. A successful exploit could allow the attacker to cause the device to reload.

Affected products

• Cisco IOS: from 3.16.8s, before 16.3.8 (fixed in 16.3.8); from 16.10.1, before 16.11.1 (fixed in 16.11.1); version 16.6.4 only; version 16.6.5 only; version 16.9.1 only; version 16.9.2 only

Published 2019-09-25. Last modified 2026-06-17.