CVE-2026-23209

Estado: ModificadaAlta (7.8)—

In the Linux kernel, the following vulnerability has been resolved:

macvlan: fix error recovery in macvlan_common_newlink()

valis provided a nice repro to crash the kernel:

ip link add p1 type veth peer p2 ip link set address 00:00:00:00:00:20 dev p1 ip link set up dev p1 ip link set up dev p2

ip link add mv0 link p2 type macvlan mode source ip link add invalid% link p2 type macvlan mode source macaddr add 00:00:00:00:00:20

ping -c1 -I p1 1.2.3.4

He also gave a very detailed analysis:

The issue is triggered when a new macvlan link is created with MACVLAN_MODE_SOURCE mode and MACVLAN_MACADDR_ADD (or MACVLAN_MACADDR_SET) parameter, lower device already has a macvlan port and register_netdevice() called from macvlan_common_newlink() fails (e.g. because of the invalid link name).

Leer descripción completaMostrar menos

In this case macvlan_hash_add_source is called from macvlan_change_sources() / macvlan_common_newlink():

This adds a reference to vlan to the port's vlan_source_hash using macvlan_source_entry.

vlan is a pointer to the priv data of the link that is being created.

When register_netdevice() fails, the error is returned from macvlan_newlink() to rtnl_newlink_create():

and free_netdev() is called, causing a kvfree() on the struct net_device that is still referenced in the source entry attached to the lower device's macvlan port.

Now all packets sent on the macvlan port with a matching source mac address will trigger a use-after-free in macvlan_forward_source().

</quote valis>

With all that, my fix is to make sure we call macvlan_flush_sources() regardless of @create value whenever "goto destroy_macvlan_port;" path is taken.

Many thanks to valis for following up on this issue.

Detalles técnicos trazas, registros y código del informe original

        if (ops->newlink)
                err = ops->newlink(dev, &params, extack);
        else
                err = register_netdevice(dev);
        if (err < 0) {
                free_netdev(dev);
                goto out;
        }

CVSS

Versión: 3.1
Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Puntuación base: 7.8

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).

🎯 Técnicas ATT&CK

Cómo se explota esta vulnerabilidad y qué consigue el atacante, en el lenguaje de MITRE ATT&CK.

ExplotaciónT1068 Exploitation for Privilege Escalationprivilege escalation85 %
Impacto principalT1059 Command and Scripting Interpreterexecution75 %
Impacto secundarioT1499.004 Application or System Exploitationimpact70 %

CVE-2026-23209 es una vulnerabilidad use-after-free (CWE-416) en el kernel Linux que requiere acceso local (AV:L, PR:L) sin interacción del usuario. Permite a un atacante local ejecutar código o causar DoS manipulando interfaces macvlan. La escalada de privilegios es viable dado el contexto del kern

Inferido por nuestro agente de análisis a partir de la descripción oficial, el vector CVSS y la CWE, y comprobado por un supervisor. Puede contener errores.

🛡️ Mitigaciones ATT&CK que cubren estas técnicas

Execution Prevention Threat Intelligence Program Restrict Web-Based Content Privileged Account Management Limit Software Installation Filter Network Traffic

Tecnologías afectadas (1)

Linux — Linux Kernel

CWE

CWE-416

Referencias

JSON original (NVD)

Mostrar

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      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nmacvlan: fix error recovery in macvlan_common_newlink()\n\nvalis provided a nice repro to crash the kernel:\n\nip link add p1 type veth peer p2\nip link set address 00:00:00:00:00:20 dev p1\nip link set up dev p1\nip link set up dev p2\n\nip link add mv0 link p2 type macvlan mode source\nip link add invalid% link p2 type macvlan mode source macaddr add 00:00:00:00:00:20\n\nping -c1 -I p1 1.2.3.4\n\nHe also gave a very detailed analysis:\n\n<quote valis>\n\nThe issue is triggered when a new macvlan link is created  with\nMACVLAN_MODE_SOURCE mode and MACVLAN_MACADDR_ADD (or\nMACVLAN_MACADDR_SET) parameter, lower device already has a macvlan\nport and register_netdevice() called from macvlan_common_newlink()\nfails (e.g. because of the invalid link name).\n\nIn this case macvlan_hash_add_source is called from\nmacvlan_change_sources() / macvlan_common_newlink():\n\nThis adds a reference to vlan to the port's vlan_source_hash using\nmacvlan_source_entry.\n\nvlan is a pointer to the priv data of the link that is being created.\n\nWhen register_netdevice() fails, the error is returned from\nmacvlan_newlink() to rtnl_newlink_create():\n\n        if (ops->newlink)\n                err = ops->newlink(dev, &params, extack);\n        else\n                err = register_netdevice(dev);\n        if (err < 0) {\n                free_netdev(dev);\n                goto out;\n        }\n\nand free_netdev() is called, causing a kvfree() on the struct\nnet_device that is still referenced in the source entry attached to\nthe lower device's macvlan port.\n\nNow all packets sent on the macvlan port with a matching source mac\naddress will trigger a use-after-free in macvlan_forward_source().\n\n</quote valis>\n\nWith all that, my fix is to make sure we call macvlan_flush_sources()\nregardless of @create value whenever \"goto destroy_macvlan_port;\"\npath is taken.\n\nMany thanks to valis for following up on this issue."
    },
    {
      "lang": "es",
      "value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\nmacvlan: arreglar la recuperación de errores en macvlan_common_newlink()\n\nvalis proporcionó una buena reproducción para colapsar el kernel:\n\nip link add p1 type veth peer p2\nip link set address 00:00:00:00:00:20 dev p1\nip link set up dev p1\nip link set up dev p2\n\nip link add mv0 link p2 type macvlan mode source\nip link add invalid% link p2 type macvlan mode source macaddr add 00:00:00:00:00:20\n\nping -c1 -I p1 1.2.3.4\n\nTambién proporcionó un análisis muy detallado:\n\n'El problema se activa cuando se crea un nuevo enlace macvlan con el modo MACVLAN_MODE_SOURCE y el parámetro MACVLAN_MACADDR_ADD (o MACVLAN_MACADDR_SET), el dispositivo inferior ya tiene un puerto macvlan y register_netdevice() llamado desde macvlan_common_newlink() falla (por ejemplo, debido al nombre de enlace no válido).\n\nEn este caso, macvlan_hash_add_source es llamado desde macvlan_change_sources() / macvlan_common_newlink():\n\nEsto añade una referencia a vlan al vlan_source_hash del puerto usando macvlan_source_entry.\n\nvlan es un puntero a los datos privados del enlace que se está creando.\n\nCuando register_netdevice() falla, el error es devuelto desde macvlan_newlink() a rtnl_newlink_create():\n\n        if (ops-&gt;newlink)\n                err = ops-&gt;newlink(dev, &amp;params, extack);\n        else\n                err = register_netdevice(dev);\n        if (err &lt; 0) {\n                free_netdev(dev);\n                goto out;\n        }\n\ny se llama a free_netdev(), causando un kvfree() en la estructura net_device que todavía está referenciada en la entrada de origen adjunta al puerto macvlan del dispositivo inferior.\n\nAhora, todos los paquetes enviados en el puerto macvlan con una dirección MAC de origen coincidente activarán un uso después de liberación en macvlan_forward_source().'\n\nCon todo eso, mi solución es asegurarme de que llamamos a macvlan_flush_sources() independientemente del valor de @create cada vez que se toma la ruta \"goto destroy_macvlan_port;\".\n\nMuchas gracias a valis por hacer seguimiento de este problema."
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