CVE-2021-1256: Cisco Secure Firewall Threat Defense

Medium severity, CVSS 6.0. EPSS: 0.5% chance of exploitation in the next 30 days.

A vulnerability in the CLI of Cisco Firepower Threat Defense (FTD) Software could allow an authenticated, local attacker to overwrite files on the file system of an affected device by using directory traversal techniques. A successful exploit could cause system instability if important system files are overwritten. This vulnerability is due to insufficient validation of user input for the file path in a specific CLI command. An attacker could exploit this vulnerability by logging in to a targeted device and issuing a specific CLI command with crafted user input. A successful exploit could allow the attacker to overwrite arbitrary files on the file system of the affected device. The attacker would need valid user credentials on the device.

Affected products

• Cisco Secure Firewall Threat Defense: up to and including 6.4.0; from 6.6.0, before 6.6.4 (fixed in 6.6.4)

Published 2021-04-29. Last modified 2026-08-11.