CVE-2026-74657
Full vulnerability record from the local CVENow database.
Description
In the Linux kernel, the following vulnerability has been resolved: ipv4: Fix fib_nlmsg_size() for RTA_VIA nexthops fib_nlmsg_size() still estimates nexthop space as if every gateway is encoded as an IPv4 RTA_GATEWAY attribute. IPv4 routes can also carry an IPv6 gateway, which fib_nexthop_info() dumps as RTA_VIA. As a result, route notifications can allocate an skb that is too small. fib_dump_info() then fails with -EMSGSIZE and rtmsg_fib() hits the WARN_ON() that marks such failures as a fib_nlmsg_size() bug. With panic_on_warn set, this becomes a kernel panic. Mirror the actual nexthop dump layout in fib_nlmsg_size(): account for IPv6 nexthop gateways dumped as RTA_VIA, for the no-header rtnexthop layout used inside RTA_MULTIPATH, and for RTA_FLOW only when it is actually present.
Severity
Not scored
CVSS score
Not available
Vulnerability status
Received
Source identifier
416baaa9-dc9f-4396-8d5f-8c081fb06d67
Published
2026-08-22 16:16:39.333000
Last modified
2026-11-06 17:19:52.760000
View original CVE JSON
{
"id": "CVE-2026-74657",
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"published": "2026-08-22T16:16:39.333",
"lastModified": "2026-11-06T17:19:52.760",
"vulnStatus": "Received",
"cveTags": [],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nipv4: Fix fib_nlmsg_size() for RTA_VIA nexthops\n\nfib_nlmsg_size() still estimates nexthop space as if every gateway is\nencoded as an IPv4 RTA_GATEWAY attribute. IPv4 routes can also carry an\nIPv6 gateway, which fib_nexthop_info() dumps as RTA_VIA.\n\nAs a result, route notifications can allocate an skb that is too small.\nfib_dump_info() then fails with -EMSGSIZE and rtmsg_fib() hits the\nWARN_ON() that marks such failures as a fib_nlmsg_size() bug. With\npanic_on_warn set, this becomes a kernel panic.\n\nMirror the actual nexthop dump layout in fib_nlmsg_size(): account for\nIPv6 nexthop gateways dumped as RTA_VIA, for the no-header rtnexthop\nlayout used inside RTA_MULTIPATH, and for RTA_FLOW only when it is\nactually present."
},
{
"lang": "es",
"value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\nipv4: Arreglo de fib_nlmsg_size() para los saltos siguientes RTA_VIA\n\nfib_nlmsg_size() todavía estima el espacio del salto siguiente como si cada puerta de enlace estuviera codificada como un atributo IPv4 RTA_GATEWAY. Las rutas IPv4 también pueden llevar una puerta de enlace IPv6, que fib_nexthop_info() vuelca como RTA_VIA.\n\nComo resultado, las notificaciones de ruta pueden asignar un skb que es demasiado pequeño. fib_dump_info() entonces falla con -EMSGSIZE y rtmsg_fib() alcanza el WARN_ON() que marca tales fallos como un error de fib_nlmsg_size(). Con panic_on_warn configurado, esto se convierte en un pánico del kernel.\n\nReflejar la disposición real del volcado del salto siguiente en fib_nlmsg_size(): tener en cuenta las puertas de enlace de salto siguiente IPv6 volcadas como RTA_VIA, para la disposición rtnexthop sin cabecera utilizada dentro de RTA_MULTIPATH, y para RTA_FLOW solo cuando está realmente presente."
}
],
"affected": [
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"affectedData": [
{
"vendor": "Linux",
"product": "Linux",
"defaultStatus": "unaffected",
"programFiles": [
"net/ipv4/fib_semantics.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"versions": [
{
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"lessThan": "57195f0ab5cfbb5ee0864e5aff15ceb48f5a5e28",
"versionType": "git",
"status": "affected"
},
{
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"lessThan": "0f0ca602941d0a81ae9514943ca06c55159c6385",
"versionType": "git",
"status": "affected"
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"status": "affected"
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{
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{
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"versionType": "git",
"status": "affected"
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{
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"versionType": "git",
"status": "affected"
}
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},
{
"vendor": "Linux",
"product": "Linux",
"defaultStatus": "affected",
"programFiles": [
"net/ipv4/fib_semantics.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"versions": [
{
"version": "5.2",
"status": "affected"
},
{
"version": "0",
"lessThan": "5.2",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "5.10.267",
"lessThanOrEqual": "5.10.*",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "5.15.216",
"lessThanOrEqual": "5.15.*",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "6.1.183",
"lessThanOrEqual": "6.1.*",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "6.6.152",
"lessThanOrEqual": "6.6.*",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "6.12.104",
"lessThanOrEqual": "6.12.*",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "6.18.45",
"lessThanOrEqual": "6.18.*",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "7.1.9",
"lessThanOrEqual": "7.1.*",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "7.2",
"lessThanOrEqual": "*",
"versionType": "original_commit_for_fix",
"status": "unaffected"
}
]
}
]
}
],
"metrics": {
"ssvcV203": [
{
"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"ssvcData": {
"timestamp": "2026-11-06T17:00:29.811370Z",
"id": "CVE-2026-74657",
"options": [
{
"exploitation": "none"
},
{
"automatable": "no"
},
{
"technicalImpact": "partial"
}
],
"role": "CISA Coordinator",
"version": "2.0.3"
}
}
]
},
"references": [
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"url": "https://git.kernel.org/stable/c/0f0ca602941d0a81ae9514943ca06c55159c6385",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
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{
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{
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"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
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{
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{
"url": "https://git.kernel.org/stable/c/57195f0ab5cfbb5ee0864e5aff15ceb48f5a5e28",
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{
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{
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}