Vulnerability Discussion

Restricting TFTP to a specific directory prevents remote users from copying, transferring, or overwriting system files. Using the "-s" option causes the TFTP service to only serve files from the given directory.

Check

Verify the TFTP daemon is configured to operate in secure mode.

Check if a TFTP server is installed with the following command:

$ sudo dnf list --installed tftp-server

Example output:

tftp-server.x86_64 5.2-35.el9.x86_64

Note: If a TFTP server is not installed, this requirement is Not Applicable.

If a TFTP server is installed, check for the server arguments with the following command:

$ systemctl cat tftp | grep ExecStart
ExecStart=/usr/sbin/in.tftpd -s /var/lib/tftpboot

If the "ExecStart" line does not have a "-s" option, and a subdirectory is not assigned, this is a finding.

Fix

Configure the TFTP daemon to operate in secure mode.

1. Find the path for the systemd service.

$ sudo systemctl show tftp | grep FragmentPath=
FragmentPath=/etc/systemd/system/tftp.service

2. Edit the ExecStart line on that file to add the -s option with a subdirectory.

ExecStart=/usr/sbin/in.tftpd -s /var/lib/tftpboot