CVE-2025-68206

Description

In the Linux kernel, the following vulnerability has been resolved:netfilter: nft_ct: add seqadj extension for natted connectionsSequence adjustment may be required for FTP traffic with PASV/EPSV modes.due to need to re-write packet payload (IP, port) on the ftp controlconnection. This can require changes to the TCP length and expectedseq / ack_seq.The easiest way to reproduce this issue is with PASV mode.Example ruleset:table inet ftp_nat { ct helper ftp_helper { type ftp protocol tcp l3proto inet } chain prerouting { type filter hook prerouting priority 0; policy accept; tcp dport 21 ct state new ct helper set ftp_helper }}table ip nat { chain prerouting { type nat hook prerouting priority -100; policy accept; tcp dport 21 dnat ip prefix to ip daddr map {192.168.100.1 : 192.168.13.2/32 } } chain postrouting { type nat hook postrouting priority 100 ; policy accept; tcp sport 21 snat ip prefix to ip saddr map {192.168.13.2 : 192.168.100.1/32 } }}Note that the ftp helper gets assigned *after* the dnat setup.The inverse (nat after helper assign) is handled by an existingcheck in nf_nat_setup_info() and will not show the problem.Topoloy: +-------------------+ +----------------------------------+ | FTP: 192.168.13.2 | <-> | NAT: 192.168.13.3, 192.168.100.1 | +-------------------+ +----------------------------------+ | +-----------------------+ | Client: 192.168.100.2 | +-----------------------+ftp nat changes do not work as expected in this case:Connected to 192.168.100.1.[..]ftp> epsvEPSV/EPRT on IPv4 off.ftp> ls227 Entering passive mode (192,168,100,1,209,129).421 Service not available, remote server has closed connection.Kernel logs:Missing nfct_seqadj_ext_add() setup callWARNING: CPU: 1 PID: 0 at net/netfilter/nf_conntrack_seqadj.c:41[..] __nf_nat_mangle_tcp_packet+0x100/0x160 [nf_nat] nf_nat_ftp+0x142/0x280 [nf_nat_ftp] help+0x4d1/0x880 [nf_conntrack_ftp] nf_confirm+0x122/0x2e0 [nf_conntrack] nf_hook_slow+0x3c/0xb0 ..Fix this by adding the required extension when a conntrack helper is assignedto a connection that has a nat binding.

Risk Information

Associated Vulnerability

Patch Details

References

https://nvd.nist.gov/vuln/detail/CVE-2023-1234
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2023-1234