DHCP server cannot execute script: permission denied exit 32512

I created a DHCP server on ubuntu 18:04 using isc-dhcp-server that normally works. I want to run a script located in /user/sbin but get error of permission denied with exit status 32512. Probably it's a permission error but I'm not expert. This is my dhcp server located in:

/etc/dhcp/dhcpd.conf

default-lease-time 86400;
max-lease-time 7200;

ignore client-updates;
authoritative;

use-host-decl-names on;
log-facility local7;


subnet 192.168.1.0 netmask 255.255.255.0 {
    range 192.168.1.101 192.168.1.150;
    option subnet-mask 255.255.255.0;
    option routers 192.168.1.3;
    option domain-name-servers 192.168.1.100;
    ddns-rev-domainname "in-addr.arpa.";
}

on commit {
    set ClientIP = binary-to-ascii(10, 8, ".", leased-address);
    set ClientMac = binary-to-ascii(16, 8, ":", substring(hardware, 1, 6));
    log(concat("Commit: IP: ", ClientIP, " Mac: ", ClientMac));
    execute("/usr/sbin/update_DB.sh", "commit", ClientIP, ClientMac);
}

/var/log/syslog

Apr  8 14:28:05 dhcp dhcpd[1223]: Commit: IP: 192.168.1.102 Mac: XXX
Apr  8 14:28:05 dhcp dhcpd[1223]: execute_statement argv[0] = /usr/sbin/update_DB.sh
Apr  8 14:28:05 dhcp dhcpd[1223]: execute_statement argv[1] = commit
Apr  8 14:28:05 dhcp dhcpd[1223]: execute_statement argv[2] = 192.168.1.102
Apr  8 14:28:05 dhcp dhcpd[1223]: execute_statement argv[3] = XXX
Apr  8 14:28:05 dhcp dhcpd[1227]: Unable to execute /usr/sbin/update_DB.sh: Permission denied
Apr  8 14:28:05 dhcp dhcpd[1223]: execute: /usr/sbin/update_DB.sh exit status 32512

anyone knows how to solve it, please? Thanks!

It's clear from your post:

Please post the output of:

ls -l /usr/sbin/update_DB.sh