Cisco fixes vulnerability that allowed criminals to remotely execute arbitrary code and control a firewall

August 1, 2021

Users are advised to install new versions of Cisco FDM On-Box, check for signs of penetration using NTA and SIEM systems


August 2, 2021 -- Cisco announced that it has fixed a vulnerability in Cisco Firepower Device Manager (FDM) On-Box discovered by Positive Technologies experts Nikita Abramov and Mikhail Klyuchnikov. This device manager is designed to locally configure Cisco Firepower NGFW firewalls. According to Forrester Research, Cisco is a recognized leader in the corporate firewall market.


Vulnerability CVE-2021-1518 gained the CVSS 3.1. score of 6.3. The flaw was discovered in REST API[1] of Cisco FDM On-Box software, and allowed an authenticated remote attacker to execute arbitrary code in the operating system of an affected device. 


Positive Technologies researcher, Nikita Abramov explains: “To exploit this vulnerability, all attackers need to do is to obtain credentials of a user with low privileges and send a specially crafted HTTP request. From a technical standpoint, the vulnerability is caused by insufficient user input validation for some REST API commands.”


Cisco FDM On-Box versions 6.3.0, 6.4.0, 6.5.0, 6.6.0, and 6.7.0 are all affected by the vulnerability. Cisco has released software updates fixing the vulnerability:, 6.4.4, and 


NTA/NDR solutions for deep traffic analysis, in particular PT Network Attack Discovery, can help detect attempts to exploit vulnerabilities in Cisco firewall. One way to detect signs of penetration is to use SIEM solutions such asMaxPatrol SIEM, which help identify suspicious behavior, register an incident, and prevent intruders from moving laterally within the corporate network.



About Positive Technologies  

Positive Technologies is a leading global provider of enterprise security solutions for vulnerability and compliance management, incident and threat analysis, and application protection. Commitment to clients and research has earned Positive Technologies a reputation as one of the foremost authorities on Industrial Control System, Banking, Telecom, Web Application, and ERP security, supported by recognition from the analyst community.



Paula Dunne


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[1] REST API is an application programming interface that uses HTTP or HTTPS requests for interaction between web services. REST API allows web clients and servers to interact with diverse web resources.