A hardcoded SSH public key in Fortinet’s Security Information and Event Management FortiSIEM can be abused to access the FortiSIEM Supervisor.
The hardcoded SSH key is for the user 'tunneluser', is the same between installs and is also stored unencrypted in the FortiSIEM image. As a result, an attacker could retrieve it and use it to sign into the FortiSIEM Supervisor without authentication.
“While the user's shell is limited to running the /opt/phoenix/phscripts/bin/tunnelshell script, SSH authentication still succeeds,” Cybera Inc Security Specialist Andrew Klaus explained.
Tracked as CVE-2019-17659, the vulnerability could lead to denial of service, security solutions provider Fortinet notes in an advisory.
The company also explains that the user 'tunneluser' only runs in a restricted shell “that lets only that user create tunnel connections from the supervisor to the originating IP.”
As such, it is possible to enable reverse-shell connections to the IP that initiated the connection. The feature, Fortinet says, is meant to enable connecting to collectors from the supervisor when a firewall exists between collector and the supervisor.
Fortinet advises customers who are not using the reverse tunnel feature to disable SSH on port 19999. The company also provides information on the steps that customers can perform on Supervisor to remove the keys associated with the 'tunneluser' account.
Moreover, the security company advises customers to also disable 'tunneluser' SSH access on port 22.
According to Klaus, customers should clear out or delete the /home/tunneluser/.ssh/authorized_keys file and also ensure that their nodes are behind firewalls with only trusted access to ports.
The security ..
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