Adversaries may abuse netbooting to load an unauthorized network device operating system from a Trivial File Transfer Protocol (TFTP) server. TFTP boot (netbooting) is commonly used by network administrators to load configuration-controlled network device images from a centralized management server. Netbooting is one option in the boot sequence and can be used to centralize, manage, and control device images.
Adversaries may manipulate the configuration on the network device specifying use of a malicious TFTP server, which may be used in conjunction with Modify System Image to load a modified image on device startup or reset. The unauthorized image allows adversaries to modify device configuration, add malicious capabilities to the device, and introduce backdoors to maintain control of the network device while minimizing detection through use of a standard functionality. This technique is similar to ROMMONkit and may result in the network device running a modified image. (Citation: Cisco Blog Legacy Device Attacks)
View in MITRE ATT&CK®| Capability ID | Capability Description | Mapping Type | ATT&CK ID | ATT&CK Name | Notes |
|---|---|---|---|---|---|
| CVE-2017-6742 | Cisco IOS and IOS XE Software SNMP Remote Code Execution Vulnerability | secondary_impact | T1542.005 | TFTP Boot |
Comments
CVE-2017-6742 is a Simple Network Management Protocol (SNMP) vulnerability in Cisco products related to a buffer overflow condition in the SNMP subsystem.
Reported by the NCSC, threat actors exploited CVE-2017-6742 to perform reconnaissance, enumerate router interfaces and deploy custom malware known as "Jaguar Tooth", as detailed in the NCSC’s Jaguar Tooth malware analysis report. This malware obtains further device information which is then exfiltrated over trivial file transfer protocol (TFTP) and enables unauthenticated access via a backdoor.
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