HGW BL1500HM Ver 002.001.013 and earlier contains a use of week credentials issue. A network-adjacent unauthenticated attacker may change the system settings.
https://www.au.com/support/service/internet/guide/modem/bl1500hm/firmware/
https://kddi-tech.com/contents/appendix_L2_06.html#20304f4c-af1b-49fd-c3b5-8d1f55fd8b4f