CVE-2025-68206 (GCVE-0-2025-68206)
Vulnerability from cvelistv5
Published
2025-12-16 13:48
Modified
2025-12-16 13:48
Severity ?
Summary
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 { 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 existing check 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> epsv EPSV/EPRT on IPv4 off. ftp> 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.
References
Impacted products
Vendor Product Version
Linux Linux Version: 1a64edf54f55d7956cf5a0d95898bc1f84f9b818
Version: 1a64edf54f55d7956cf5a0d95898bc1f84f9b818
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/netfilter/nft_ct.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "2b52d89cbbb0dbe3e948d8d9a91e704316dccfe6",
              "status": "affected",
              "version": "1a64edf54f55d7956cf5a0d95898bc1f84f9b818",
              "versionType": "git"
            },
            {
              "lessThan": "90918e3b6404c2a37837b8f11692471b4c512de2",
              "status": "affected",
              "version": "1a64edf54f55d7956cf5a0d95898bc1f84f9b818",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "net/netfilter/nft_ct.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "4.12"
            },
            {
              "lessThan": "4.12",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.17.*",
              "status": "unaffected",
              "version": "6.17.9",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "6.18",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.17.9",
                  "versionStartIncluding": "4.12",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18",
                  "versionStartIncluding": "4.12",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnetfilter: nft_ct: add seqadj extension for natted connections\n\nSequence adjustment may be required for FTP traffic with PASV/EPSV modes.\ndue to need to re-write packet payload (IP, port) on the ftp control\nconnection. This can require changes to the TCP length and expected\nseq / ack_seq.\n\nThe easiest way to reproduce this issue is with PASV mode.\nExample ruleset:\ntable inet ftp_nat {\n        ct helper ftp_helper {\n                type \"ftp\" protocol tcp\n                l3proto inet\n        }\n\n        chain prerouting {\n                type filter hook prerouting priority 0; policy accept;\n                tcp dport 21 ct state new ct helper set \"ftp_helper\"\n        }\n}\ntable ip nat {\n        chain prerouting {\n                type nat hook prerouting priority -100; policy accept;\n                tcp dport 21 dnat ip prefix to ip daddr map {\n\t\t\t192.168.100.1 : 192.168.13.2/32 }\n        }\n\n        chain postrouting {\n                type nat hook postrouting priority 100 ; policy accept;\n                tcp sport 21 snat ip prefix to ip saddr map {\n\t\t\t192.168.13.2 : 192.168.100.1/32 }\n        }\n}\n\nNote that the ftp helper gets assigned *after* the dnat setup.\n\nThe inverse (nat after helper assign) is handled by an existing\ncheck in nf_nat_setup_info() and will not show the problem.\n\nTopoloy:\n\n +-------------------+     +----------------------------------+\n | FTP: 192.168.13.2 | \u003c-\u003e | NAT: 192.168.13.3, 192.168.100.1 |\n +-------------------+     +----------------------------------+\n                                      |\n                         +-----------------------+\n                         | Client: 192.168.100.2 |\n                         +-----------------------+\n\nftp nat changes do not work as expected in this case:\nConnected to 192.168.100.1.\n[..]\nftp\u003e epsv\nEPSV/EPRT on IPv4 off.\nftp\u003e ls\n227 Entering passive mode (192,168,100,1,209,129).\n421 Service not available, remote server has closed connection.\n\nKernel logs:\nMissing nfct_seqadj_ext_add() setup call\nWARNING: CPU: 1 PID: 0 at net/netfilter/nf_conntrack_seqadj.c:41\n[..]\n __nf_nat_mangle_tcp_packet+0x100/0x160 [nf_nat]\n nf_nat_ftp+0x142/0x280 [nf_nat_ftp]\n help+0x4d1/0x880 [nf_conntrack_ftp]\n nf_confirm+0x122/0x2e0 [nf_conntrack]\n nf_hook_slow+0x3c/0xb0\n ..\n\nFix this by adding the required extension when a conntrack helper is assigned\nto a connection that has a nat binding."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2025-12-16T13:48:33.763Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/2b52d89cbbb0dbe3e948d8d9a91e704316dccfe6"
        },
        {
          "url": "https://git.kernel.org/stable/c/90918e3b6404c2a37837b8f11692471b4c512de2"
        }
      ],
      "title": "netfilter: nft_ct: add seqadj extension for natted connections",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2025-68206",
    "datePublished": "2025-12-16T13:48:33.763Z",
    "dateReserved": "2025-12-16T13:41:40.255Z",
    "dateUpdated": "2025-12-16T13:48:33.763Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "nvd": "{\"cve\":{\"id\":\"CVE-2025-68206\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2025-12-16T14:15:53.487\",\"lastModified\":\"2025-12-18T15:08:25.907\",\"vulnStatus\":\"Awaiting Analysis\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"In the Linux kernel, the following vulnerability has been resolved:\\n\\nnetfilter: nft_ct: add seqadj extension for natted connections\\n\\nSequence adjustment may be required for FTP traffic with PASV/EPSV modes.\\ndue to need to re-write packet payload (IP, port) on the ftp control\\nconnection. This can require changes to the TCP length and expected\\nseq / ack_seq.\\n\\nThe easiest way to reproduce this issue is with PASV mode.\\nExample ruleset:\\ntable inet ftp_nat {\\n        ct helper ftp_helper {\\n                type \\\"ftp\\\" protocol tcp\\n                l3proto inet\\n        }\\n\\n        chain prerouting {\\n                type filter hook prerouting priority 0; policy accept;\\n                tcp dport 21 ct state new ct helper set \\\"ftp_helper\\\"\\n        }\\n}\\ntable ip nat {\\n        chain prerouting {\\n                type nat hook prerouting priority -100; policy accept;\\n                tcp dport 21 dnat ip prefix to ip daddr map {\\n\\t\\t\\t192.168.100.1 : 192.168.13.2/32 }\\n        }\\n\\n        chain postrouting {\\n                type nat hook postrouting priority 100 ; policy accept;\\n                tcp sport 21 snat ip prefix to ip saddr map {\\n\\t\\t\\t192.168.13.2 : 192.168.100.1/32 }\\n        }\\n}\\n\\nNote that the ftp helper gets assigned *after* the dnat setup.\\n\\nThe inverse (nat after helper assign) is handled by an existing\\ncheck in nf_nat_setup_info() and will not show the problem.\\n\\nTopoloy:\\n\\n +-------------------+     +----------------------------------+\\n | FTP: 192.168.13.2 | \u003c-\u003e | NAT: 192.168.13.3, 192.168.100.1 |\\n +-------------------+     +----------------------------------+\\n                                      |\\n                         +-----------------------+\\n                         | Client: 192.168.100.2 |\\n                         +-----------------------+\\n\\nftp nat changes do not work as expected in this case:\\nConnected to 192.168.100.1.\\n[..]\\nftp\u003e epsv\\nEPSV/EPRT on IPv4 off.\\nftp\u003e ls\\n227 Entering passive mode (192,168,100,1,209,129).\\n421 Service not available, remote server has closed connection.\\n\\nKernel logs:\\nMissing nfct_seqadj_ext_add() setup call\\nWARNING: CPU: 1 PID: 0 at net/netfilter/nf_conntrack_seqadj.c:41\\n[..]\\n __nf_nat_mangle_tcp_packet+0x100/0x160 [nf_nat]\\n nf_nat_ftp+0x142/0x280 [nf_nat_ftp]\\n help+0x4d1/0x880 [nf_conntrack_ftp]\\n nf_confirm+0x122/0x2e0 [nf_conntrack]\\n nf_hook_slow+0x3c/0xb0\\n ..\\n\\nFix this by adding the required extension when a conntrack helper is assigned\\nto a connection that has a nat binding.\"}],\"metrics\":{},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/2b52d89cbbb0dbe3e948d8d9a91e704316dccfe6\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/90918e3b6404c2a37837b8f11692471b4c512de2\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}"
  }
}


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