CVE-2021-1256: 
Cisco Firepower Threat Defense (FTD) vulnerability analysis and mitigation

A vulnerability in the Command Line Interface (CLI) of Cisco Firepower Threat Defense (FTD) Software was discovered, identified as CVE-2021-1256. The vulnerability was first published on April 28, 2021, and affects Cisco FTD Software releases 6.4.0 and later. This security flaw was discovered during internal security testing by Ilkin Gasimov of Cisco (Cisco Advisory).

The vulnerability stems from insufficient validation of user input for file paths in specific CLI commands. It has been assigned CWE-552 and received a CVSS v3.1 base score of 6.0 (CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:H/A:H/E:X/RL:X/RC:X). The vulnerability allows for directory traversal techniques to be employed, potentially leading to unauthorized file system modifications (Cisco Advisory).

A successful exploitation of this vulnerability could allow an authenticated, local attacker to overwrite arbitrary files on the affected device's file system. This could potentially lead to system instability if critical system files are overwritten (Cisco Advisory).

Cisco has released software updates to address this vulnerability in FTD Software releases 6.6.4 and 6.7.0 and later. While the initial fix was included in release 6.6.3, version 6.6.4 is recommended due to upgrade issues. Additionally, a fix was planned for release 6.4.0.12 in May 2021. No workarounds are available for this vulnerability (Cisco Advisory).