CVE-2025-68206 (GCVE-0-2025-68206)

Vulnerability from cvelistv5 – Published: 2025-12-16 13:48 – Updated: 2026-05-11 21:48
VLAI
Title
netfilter: nft_ct: add seqadj extension for natted connections
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.
Severity
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: 1a64edf54f55d7956cf5a0d95898bc1f84f9b818 , < 83273af0b60c093ba0085c205864d8542e1b1653 (git)
Affected: 1a64edf54f55d7956cf5a0d95898bc1f84f9b818 , < b19492c25eff04852e0cb58f9bb8238b6695ed2d (git)
Affected: 1a64edf54f55d7956cf5a0d95898bc1f84f9b818 , < 4de80f0dc3868408dd7fe9817e507123c9dd8bb0 (git)
Affected: 1a64edf54f55d7956cf5a0d95898bc1f84f9b818 , < b477ef7fa612fa45b6b3134d90d1eeb09396500a (git)
Affected: 1a64edf54f55d7956cf5a0d95898bc1f84f9b818 , < 4ab2cd906e4e1a19ddbda6eb532851b0e9cda110 (git)
Affected: 1a64edf54f55d7956cf5a0d95898bc1f84f9b818 , < 2b52d89cbbb0dbe3e948d8d9a91e704316dccfe6 (git)
Affected: 1a64edf54f55d7956cf5a0d95898bc1f84f9b818 , < 90918e3b6404c2a37837b8f11692471b4c512de2 (git)
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Linux Linux Affected: 4.12
Unaffected: 0 , < 4.12 (semver)
Unaffected: 5.10.253 , ≤ 5.10.* (semver)
Unaffected: 5.15.203 , ≤ 5.15.* (semver)
Unaffected: 6.1.167 , ≤ 6.1.* (semver)
Unaffected: 6.6.130 , ≤ 6.6.* (semver)
Unaffected: 6.12.64 , ≤ 6.12.* (semver)
Unaffected: 6.17.9 , ≤ 6.17.* (semver)
Unaffected: 6.18 , ≤ * (original_commit_for_fix)
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{
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          "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": "2026-05-11T21:48:46.075Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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          "url": "https://git.kernel.org/stable/c/83273af0b60c093ba0085c205864d8542e1b1653"
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          "url": "https://git.kernel.org/stable/c/4de80f0dc3868408dd7fe9817e507123c9dd8bb0"
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        },
        {
          "url": "https://git.kernel.org/stable/c/90918e3b6404c2a37837b8f11692471b4c512de2"
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      ],
      "title": "netfilter: nft_ct: add seqadj extension for natted connections",
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    "assignerShortName": "Linux",
    "cveId": "CVE-2025-68206",
    "datePublished": "2025-12-16T13:48:33.763Z",
    "dateReserved": "2025-12-16T13:41:40.255Z",
    "dateUpdated": "2026-05-11T21:48:46.075Z",
    "state": "PUBLISHED"
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      "cve": "CVE-2025-68206",
      "date": "2026-06-07",
      "epss": "0.00066",
      "percentile": "0.20692"
    },
    "nvd": "{\"cve\":{\"id\":\"CVE-2025-68206\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2025-12-16T14:15:53.487\",\"lastModified\":\"2026-04-18T09:16:12.780\",\"vulnStatus\":\"Deferred\",\"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/4ab2cd906e4e1a19ddbda6eb532851b0e9cda110\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/4de80f0dc3868408dd7fe9817e507123c9dd8bb0\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/83273af0b60c093ba0085c205864d8542e1b1653\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/90918e3b6404c2a37837b8f11692471b4c512de2\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/b19492c25eff04852e0cb58f9bb8238b6695ed2d\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/b477ef7fa612fa45b6b3134d90d1eeb09396500a\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}"
  }
}


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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

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Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.