{"id":"DEBIAN-CVE-2025-68206","details":"In the Linux kernel, the following vulnerability has been resolved:  netfilter: nft_ct: add seqadj extension for natted connections  Sequence adjustment may be required for FTP traffic with PASV/EPSV modes. due to need to re-write packet payload (IP, port) on the ftp control connection. This can require changes to the TCP length and expected seq / 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 { \t\t\t192.168.100.1 : 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 { \t\t\t192.168.13.2 : 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 existing check in nf_nat_setup_info() and will not show the problem.  Topoloy:   +-------------------+     +----------------------------------+  | FTP: 192.168.13.2 | \u003c-\u003e | 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\u003e epsv EPSV/EPRT on IPv4 off. ftp\u003e ls 227 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 call WARNING: 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 assigned to a connection that has a nat binding.","modified":"2026-09-01T16:06:21.242443757Z","published":"2025-12-16T14:15:53.487Z","upstream":["CVE-2025-68206"],"references":[{"type":"ADVISORY","url":"https://security-tracker.debian.org/tracker/CVE-2025-68206"}],"affected":[{"package":{"name":"linux","ecosystem":"Debian:12","purl":"pkg:deb/debian/linux?arch=source&distro=bookworm"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.1.170-1"}]}],"versions":["6.1.106-1","6.1.106-2","6.1.106-3","6.1.112-1","6.1.115-1","6.1.119-1","6.1.123-1","6.1.124-1","6.1.128-1","6.1.129-1","6.1.133-1","6.1.135-1","6.1.137-1","6.1.139-1","6.1.140-1","6.1.147-1","6.1.148-1","6.1.153-1","6.1.158-1","6.1.159-1","6.1.162-1","6.1.164-1","6.1.27-1","6.1.37-1","6.1.38-1","6.1.38-2","6.1.38-2~bpo11+1","6.1.38-3","6.1.38-4","6.1.38-4~bpo11+1","6.1.52-1","6.1.55-1","6.1.55-1~bpo11+1","6.1.64-1","6.1.66-1","6.1.67-1","6.1.69-1","6.1.69-1~bpo11+1","6.1.76-1","6.1.76-1~bpo11+1","6.1.82-1","6.1.85-1","6.1.90-1","6.1.90-1~bpo11+1","6.1.94-1","6.1.94-1~bpo11+1","6.1.98-1","6.1.99-1"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2025-68206.json"}},{"package":{"name":"linux","ecosystem":"Debian:13","purl":"pkg:deb/debian/linux?arch=source&distro=trixie"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.12.69-1"}]}],"versions":["6.12.38-1","6.12.41-1","6.12.43-1","6.12.43-1~bpo12+1","6.12.48-1","6.12.57-1","6.12.57-1~bpo12+1","6.12.63-1","6.12.63-1~bpo12+1","6.12.69-1~bpo12+1"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2025-68206.json"}},{"package":{"name":"linux","ecosystem":"Debian:14","purl":"pkg:deb/debian/linux?arch=source&distro=forky"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.17.9-1"}]}],"versions":["6.12.100-1","6.12.101-1","6.12.105-1","6.12.107-1","6.12.38-1","6.12.41-1","6.12.43-1","6.12.43-1~bpo12+1","6.12.48-1","6.12.57-1","6.12.57-1~bpo12+1","6.12.63-1","6.12.63-1~bpo12+1","6.12.69-1","6.12.69-1~bpo12+1","6.12.73-1","6.12.73-1~bpo12+1","6.12.74-1","6.12.74-2","6.12.74-2~bpo12+1","6.12.85-1","6.12.85-1~bpo12+1","6.12.86-1","6.12.86-1~bpo12+1","6.12.88-1","6.12.88-1~bpo12+1","6.12.90-1","6.12.90-1~bpo12+1","6.12.90-2","6.12.90-2~bpo12+1","6.12.94-1","6.12.94-1~bpo12+1","6.12.95-1","6.12.95-1~bpo12+1","6.12.96-1","6.13.10-1~exp1","6.13.11-1~exp1","6.13.2-1~exp1","6.13.3-1~exp1","6.13.4-1~exp1","6.13.5-1~exp1","6.13.6-1~exp1","6.13.7-1~exp1","6.13.8-1~exp1","6.13.9-1~exp1","6.13~rc6-1~exp1","6.13~rc7-1~exp1","6.14.3-1~exp1","6.14.5-1~exp1","6.14.6-1~exp1","6.15-1~exp1","6.15.1-1~exp1","6.15.2-1~exp1","6.15.3-1~exp1","6.15.4-1~exp1","6.15.5-1~exp1","6.15.6-1~exp1","6.15~rc7-1~exp1","6.16-1~exp1","6.16.1-1~exp1","6.16.10-1","6.16.11-1","6.16.12-1","6.16.12-1~bpo13+1","6.16.12-2","6.16.3-1","6.16.3-1~bpo13+1","6.16.5-1","6.16.6-1","6.16.7-1","6.16.8-1","6.16.9-1","6.16~rc7-1~exp1","6.17.2-1~exp1","6.17.5-1~exp1","6.17.6-1","6.17.7-1","6.17.7-2","6.17.8-1","6.17.8-1~bpo13+1"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2025-68206.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"}]}