SNMP RCE
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SNMP RCE
SNMP can be exploited by an attacker if the administrator overlooks its default configuration on the device or server. By abusing SNMP community with write permissions (rwcommunity) on a Linux operating system, the attacker can execute commands on the server.
Extending Services with Additional Commands
To extend SNMP services and add extra commands, it is possible to append new rows to the "nsExtendObjects" table. This can be achieved by using the snmpset
command and providing the necessary parameters, including the absolute path to the executable and the command to be executed:
Injecting Commands for Execution
Injecting commands to run on the SNMP service requires the existence and executability of the called binary/script. The NET-SNMP-EXTEND-MIB
mandates providing the absolute path to the executable.
To confirm the execution of the injected command, the snmpwalk
command can be used to enumerate the SNMP service. The output will display the command and its associated details, including the absolute path:
Running the Injected Commands
When the injected command is read, it is executed. This behavior is known as run-on-read()
The execution of the command can be observed during the snmpwalk read.
Gaining Server Shell with SNMP
To gain control over the server and obtain a server shell, a python script developed by mxrch can be utilized from https://github.com/mxrch/snmp-shell.git.
Alternatively, a reverse shell can be manually created by injecting a specific command into SNMP. This command, triggered by the snmpwalk, establishes a reverse shell connection to the attacker's machine, enabling control over the victim machine. You can install the pre-requisite to run this:
Or a reverse shell:
References
Learn & practice AWS Hacking:HackTricks Training AWS Red Team Expert (ARTE)
Learn & practice GCP Hacking:
HackTricks Training GCP Red Team Expert (GRTE)
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