CVE-2025-68206
Estado: AplazadaAlta (7.5)—
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.
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 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.
Leer descripción completaMostrar menos
Fix this by adding the required extension when a conntrack helper is assigned to a connection that has a nat binding.
Detalles técnicos trazas, registros y código del informe original
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 }
}
}
+-------------------+ +----------------------------------+
| FTP: 192.168.13.2 | <-> | NAT: 192.168.13.3, 192.168.100.1 |
+-------------------+ +----------------------------------+
|
+-----------------------+
| Client: 192.168.100.2 |
+-----------------------+
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
..CVSS
- Versión: 3.1
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- Puntuación base: 7.5
Probabilidad de explotación (EPSS)
- Probabilidad de explotación en los próximos 30 días: 0.69%
- Percentil entre todas las CVEs puntuadas: 51
- Fecha de la puntuación: 5/10/2026
EPSS (Exploit Prediction Scoring System, de FIRST) estima la probabilidad de que una vulnerabilidad sea explotada en 30 días. Complementa a CVSS (impacto) y a CISA KEV (explotación confirmada).
🎯 Técnicas ATT&CK
Cómo se explota esta vulnerabilidad y qué consigue el atacante, en el lenguaje de MITRE ATT&CK.
- Explotación
T1190Exploit Public-Facing Applicationinitial access60 % - Impacto principal
T1499Endpoint Denial of Serviceimpact55 %
Inferido por reglas deterministas a partir del vector CVSS y la CWE. Solo orientativo.
🛡️ Mitigaciones ATT&CK que cubren estas técnicas
Tecnologías afectadas (1)
⚠ Inferidas por IA a partir de la descripción — NVD aún no ha analizado esta CVE; no son CPE verificados.
Referencias
- https://git.kernel.org/stable/c/2b52d89cbbb0dbe3e948d8d9a91e704316dccfe6
- https://git.kernel.org/stable/c/4ab2cd906e4e1a19ddbda6eb532851b0e9cda110
- https://git.kernel.org/stable/c/4de80f0dc3868408dd7fe9817e507123c9dd8bb0
- https://git.kernel.org/stable/c/83273af0b60c093ba0085c205864d8542e1b1653
- https://git.kernel.org/stable/c/90918e3b6404c2a37837b8f11692471b4c512de2
- https://git.kernel.org/stable/c/b19492c25eff04852e0cb58f9bb8238b6695ed2d
- https://git.kernel.org/stable/c/b477ef7fa612fa45b6b3134d90d1eeb09396500a
- https://cert-portal.siemens.com/productcert/html/ssa-019113.html
- https://cert-portal.siemens.com/productcert/html/ssa-082556.html
JSON original (NVD)
Mostrar
{
"id": "CVE-2025-68206",
"cveTags": [],
"metrics": {
"cvssMetricV31": [
{
"type": "Secondary",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"cvssData": {
"scope": "UNCHANGED",
"version": "3.1",
"baseScore": 7.5,
"attackVector": "NETWORK",
"baseSeverity": "HIGH",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
"integrityImpact": "NONE",
"userInteraction": "NONE",
"attackComplexity": "LOW",
"availabilityImpact": "HIGH",
"privilegesRequired": "NONE",
"confidentialityImpact": "NONE"
},
"impactScore": 3.6,
"exploitabilityScore": 3.9
}
]
},
"affected": [
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"affectedData": [
{
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"vendor": "Linux",
"product": "Linux",
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"status": "affected",
"version": "1a64edf54f55d7956cf5a0d95898bc1f84f9b818",
"lessThan": "83273af0b60c093ba0085c205864d8542e1b1653",
"versionType": "git"
},
{
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},
{
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"versionType": "git"
},
{
"status": "affected",
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"versionType": "git"
},
{
"status": "affected",
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"lessThan": "4ab2cd906e4e1a19ddbda6eb532851b0e9cda110",
"versionType": "git"
},
{
"status": "affected",
"version": "1a64edf54f55d7956cf5a0d95898bc1f84f9b818",
"lessThan": "2b52d89cbbb0dbe3e948d8d9a91e704316dccfe6",
"versionType": "git"
},
{
"status": "affected",
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"lessThan": "90918e3b6404c2a37837b8f11692471b4c512de2",
"versionType": "git"
}
],
"programFiles": [
"net/netfilter/nft_ct.c"
],
"defaultStatus": "unaffected"
},
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "4.12"
},
{
"status": "unaffected",
"version": "0",
"lessThan": "4.12",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "5.10.253",
"versionType": "semver",
"lessThanOrEqual": "5.10.*"
},
{
"status": "unaffected",
"version": "5.15.203",
"versionType": "semver",
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},
{
"status": "unaffected",
"version": "6.1.167",
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},
{
"status": "unaffected",
"version": "6.6.130",
"versionType": "semver",
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},
{
"status": "unaffected",
"version": "6.12.64",
"versionType": "semver",
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},
{
"status": "unaffected",
"version": "6.17.9",
"versionType": "semver",
"lessThanOrEqual": "6.17.*"
},
{
"status": "unaffected",
"version": "6.18",
"versionType": "original_commit_for_fix",
"lessThanOrEqual": "*"
}
],
"programFiles": [
"net/netfilter/nft_ct.c"
],
"defaultStatus": "affected"
}
]
},
{
"source": "0b142b55-0307-4c5a-b3c9-f314f3fb7c5e",
"affectedData": [
{
"vendor": "Siemens",
"product": "SIMATIC S7-1500 CPU 1518-4 PN/DP MFP",
"versions": [
{
"status": "affected",
"version": "V3.1.6",
"lessThan": "*",
"versionType": "custom"
}
],
"defaultStatus": "unknown"
},
{
"vendor": "Siemens",
"product": "SIMATIC S7-1500 CPU 1518-4 PN/DP MFP",
"versions": [
{
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"lessThan": "*",
"versionType": "custom"
}
],
"defaultStatus": "unknown"
},
{
"vendor": "Siemens",
"product": "SIMATIC S7-1500 CPU 1518-4 PN/DP MFP",
"versions": [
{
"status": "affected",
"version": "V3.1.6",
"lessThan": "*",
"versionType": "custom"
}
],
"defaultStatus": "unknown"
},
{
"vendor": "Siemens",
"product": "SIMATIC S7-1500 CPU 1518-4 PN/DP MFP",
"versions": [
{
"status": "affected",
"version": "V3.1.5",
"lessThan": "*",
"versionType": "custom"
}
],
"defaultStatus": "unknown"
},
{
"vendor": "Siemens",
"product": "SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP",
"versions": [
{
"status": "affected",
"version": "V3.1.6",
"lessThan": "*",
"versionType": "custom"
}
],
"defaultStatus": "unknown"
},
{
"vendor": "Siemens",
"product": "SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP",
"versions": [
{
"status": "affected",
"version": "V3.1.5",
"lessThan": "*",
"versionType": "custom"
}
],
"defaultStatus": "unknown"
},
{
"vendor": "Siemens",
"product": "SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP",
"versions": [
{
"status": "affected",
"version": "V3.1.6",
"lessThan": "*",
"versionType": "custom"
}
],
"defaultStatus": "unknown"
},
{
"vendor": "Siemens",
"product": "SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP",
"versions": [
{
"status": "affected",
"version": "V3.1.5",
"lessThan": "*",
"versionType": "custom"
}
],
"defaultStatus": "unknown"
},
{
"vendor": "Siemens",
"product": "SIPLUS S7-1500 CPU 1518-4 PN/DP MFP",
"versions": [
{
"status": "affected",
"version": "V3.1.6",
"lessThan": "*",
"versionType": "custom"
}
],
"defaultStatus": "unknown"
},
{
"vendor": "Siemens",
"product": "SIPLUS S7-1500 CPU 1518-4 PN/DP MFP",
"versions": [
{
"status": "affected",
"version": "V3.1.5",
"lessThan": "*",
"versionType": "custom"
}
],
"defaultStatus": "unknown"
}
]
}
],
"published": "2025-12-16T14:15:53.487",
"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"
},
{
"url": "https://cert-portal.siemens.com/productcert/html/ssa-019113.html",
"source": "0b142b55-0307-4c5a-b3c9-f314f3fb7c5e"
},
{
"url": "https://cert-portal.siemens.com/productcert/html/ssa-082556.html",
"source": "0b142b55-0307-4c5a-b3c9-f314f3fb7c5e"
}
],
"vulnStatus": "Deferred",
"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 | <-> | 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> epsv\nEPSV/EPRT on IPv4 off.\nftp> 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."
}
],
"lastModified": "2026-07-30T06:24:33.213",
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}