CVE-2026-23300
Estado: ModificadaMedia (5.5)—
In the Linux kernel, the following vulnerability has been resolved:
net: ipv6: fix panic when IPv4 route references loopback IPv6 nexthop
When a standalone IPv6 nexthop object is created with a loopback device (e.g., "ip -6 nexthop add id 100 dev lo"), fib6_nh_init() misclassifies it as a reject route. This is because nexthop objects have no destination prefix (fc_dst=::), causing fib6_is_reject() to match any loopback nexthop. The reject path skips fib_nh_common_init(), leaving nhc_pcpu_rth_output unallocated. If an IPv4 route later references this nexthop, __mkroute_output() dereferences NULL nhc_pcpu_rth_output and panics.
Leer descripción completaMostrar menos
Simplify the check in fib6_nh_init() to only match explicit reject routes (RTF_REJECT) instead of using fib6_is_reject(). The loopback promotion heuristic in fib6_is_reject() is handled separately by ip6_route_info_create_nh(). After this change, the three cases behave as follows:
Detalles técnicos trazas, registros y código del informe original
1. Explicit reject route ("ip -6 route add unreachable 2001:db8::/64"):
RTF_REJECT is set, enters reject path, skips fib_nh_common_init().
No behavior change.
2. Implicit loopback reject route ("ip -6 route add 2001:db8::/32 dev lo"):
RTF_REJECT is not set, takes normal path, fib_nh_common_init() is
called. ip6_route_info_create_nh() still promotes it to reject
afterward. nhc_pcpu_rth_output is allocated but unused, which is
harmless.
3. Standalone nexthop object ("ip -6 nexthop add id 100 dev lo"):
RTF_REJECT is not set, takes normal path, fib_nh_common_init() is
called. nhc_pcpu_rth_output is properly allocated, fixing the crash
when IPv4 routes reference this nexthop.CVSS
- Versión: 3.1
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
- Puntuación base: 5.5
Probabilidad de explotación (EPSS)
- Probabilidad de explotación en los próximos 30 días: 0.13%
- Percentil entre todas las CVEs puntuadas: 2
- Fecha de la puntuación: 6/10/2026
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).
Tecnologías afectadas (1)
CWE
- CWE-476
Referencias
- https://git.kernel.org/stable/c/21ec92774d1536f71bdc90b0e3d052eff99cf093
- https://git.kernel.org/stable/c/607e68c1b7c5a30c795571be1906d716e989a644
- https://git.kernel.org/stable/c/8650db85b4259d2885d2a80fbc2317ce24194133
- https://git.kernel.org/stable/c/b299121e7453d23faddf464087dff513a495b4fc
- https://git.kernel.org/stable/c/b3b5a037d520afe3d5276e653bc0ff516bbda34c
- https://git.kernel.org/stable/c/b5062fc2150614c9ea8a611c2e0cb6e047ebfa3a
- https://git.kernel.org/stable/c/c11d7c56c2076ee9cd72004f1976fe0734df2ae9
- https://git.kernel.org/stable/c/f7c9f8e3607440fe39300efbaf46cf7b5eecb23f
- https://cert-portal.siemens.com/productcert/html/ssa-019113.html
- https://cert-portal.siemens.com/productcert/html/ssa-082556.html
JSON original (NVD)
Mostrar
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"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: ipv6: fix panic when IPv4 route references loopback IPv6 nexthop\n\nWhen a standalone IPv6 nexthop object is created with a loopback device\n(e.g., \"ip -6 nexthop add id 100 dev lo\"), fib6_nh_init() misclassifies\nit as a reject route. This is because nexthop objects have no destination\nprefix (fc_dst=::), causing fib6_is_reject() to match any loopback\nnexthop. The reject path skips fib_nh_common_init(), leaving\nnhc_pcpu_rth_output unallocated. If an IPv4 route later references this\nnexthop, __mkroute_output() dereferences NULL nhc_pcpu_rth_output and\npanics.\n\nSimplify the check in fib6_nh_init() to only match explicit reject\nroutes (RTF_REJECT) instead of using fib6_is_reject(). The loopback\npromotion heuristic in fib6_is_reject() is handled separately by\nip6_route_info_create_nh(). After this change, the three cases behave\nas follows:\n\n1. Explicit reject route (\"ip -6 route add unreachable 2001:db8::/64\"):\n RTF_REJECT is set, enters reject path, skips fib_nh_common_init().\n No behavior change.\n\n2. Implicit loopback reject route (\"ip -6 route add 2001:db8::/32 dev lo\"):\n RTF_REJECT is not set, takes normal path, fib_nh_common_init() is\n called. ip6_route_info_create_nh() still promotes it to reject\n afterward. nhc_pcpu_rth_output is allocated but unused, which is\n harmless.\n\n3. Standalone nexthop object (\"ip -6 nexthop add id 100 dev lo\"):\n RTF_REJECT is not set, takes normal path, fib_nh_common_init() is\n called. nhc_pcpu_rth_output is properly allocated, fixing the crash\n when IPv4 routes reference this nexthop."
},
{
"lang": "es",
"value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\nnet: ipv6: corrige el pánico cuando una ruta IPv4 referencia un nexthop IPv6 de loopback\n\nCuando se crea un objeto nexthop IPv6 independiente con un dispositivo de loopback (p. ej., 'ip -6 nexthop add id 100 dev lo'), fib6_nh_init() lo clasifica erróneamente como una ruta de rechazo. Esto se debe a que los objetos nexthop no tienen prefijo de destino (fc_dst=::), lo que hace que fib6_is_reject() coincida con cualquier nexthop de loopback. La ruta de rechazo omite fib_nh_common_init(), dejando nhc_pcpu_rth_output sin asignar. Si una ruta IPv4 referencia posteriormente este nexthop, __mkroute_output() desreferencia nhc_pcpu_rth_output NULL y entra en pánico.\n\nSimplificar la verificación en fib6_nh_init() para que solo coincida con rutas de rechazo explícitas (RTF_REJECT) en lugar de usar fib6_is_reject(). La heurística de promoción de loopback en fib6_is_reject() se maneja por separado por ip6_route_info_create_nh(). Después de este cambio, los tres casos se comportan de la siguiente manera:\n\n1. Ruta de rechazo explícita ('ip -6 route add unreachable 2001:db8::/64'):\n RTF_REJECT está configurado, entra en la ruta de rechazo, omite fib_nh_common_init().\n Sin cambio de comportamiento.\n\n2. Ruta de rechazo de loopback implícita ('ip -6 route add 2001:db8::/32 dev lo'):\n RTF_REJECT no está configurado, toma la ruta normal, se llama a fib_nh_common_init().\n ip6_route_info_create_nh() aún lo promueve a rechazo posteriormente. nhc_pcpu_rth_output se asigna pero no se usa, lo cual es inofensivo.\n\n3. Objeto nexthop independiente ('ip -6 nexthop add id 100 dev lo'):\n RTF_REJECT no está configurado, toma la ruta normal, se llama a fib_nh_common_init().\n nhc_pcpu_rth_output se asigna correctamente, corrigiendo el fallo cuando las rutas IPv4 referencian este nexthop."
}
],
"lastModified": "2026-07-14T13:18:29.393",
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