So, on this server legacy iptable modules are being loaded in the kernel. Maybe some change in your server provider? Cloudron doesn't configure or load these modules (cloudron uses nft backend for iptables). Docker is not configuring iptables properly because of this.
root@vmi3573607:~# lsmod | grep -E 'iptable_|ip6table_'
ip6table_filter 12288 0
ip6_tables 36864 1 ip6table_filter
iptable_filter 12288 0
iptable_nat 12288 0
nf_nat 61440 5 xt_nat,nft_chain_nat,iptable_nat,xt_MASQUERADE,xt_REDIRECT
ip_tables 32768 2 iptable_filter,iptable_nat
x_tables 65536 18 ip6table_filter,xt_conntrack,iptable_filter,nft_compat,xt_LOG,xt_multiport,xt_tcpudp,xt_hashlimit,xt_addrtype,xt_recent,xt_nat,xt_set,ip6_tables,ip_tables,iptable_nat,xt_limit,xt_MASQUERADE,xt_REDIRECT
root@vmi3573607:~# cat /proc/net/ip_tables_names /proc/net/ip6_tables_names
filter
nat
filter
I manually unloaded them and it work again:
sudo modprobe -r iptable_nat iptable_filter ip6table_filter
Could an agent or something have loaded these legacy modules?
