CVE-2022-49006
Estado: ModificadaAlta (7.8)—
In the Linux kernel, the following vulnerability has been resolved:
tracing: Free buffers when a used dynamic event is removed
After 65536 dynamic events have been added and removed, the "type" field of the event then uses the first type number that is available (not currently used by other events). A type number is the identifier of the binary blobs in the tracing ring buffer (known as events) to map them to logic that can parse the binary blob.
The issue is that if a dynamic event (like a kprobe event) is traced and is in the ring buffer, and then that event is removed (because it is dynamic, which means it can be created and destroyed), if another dynamic event is created that has the same number that new event's logic on parsing the binary blob will be used.
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To show how this can be an issue, the following can crash the kernel:
# cd /sys/kernel/tracing # for i in `seq 65536`; do echo 'p:kprobes/foo do_sys_openat2 $arg1:u32' > kprobe_events # done
For every iteration of the above, the writing to the kprobe_events will remove the old event and create a new one (with the same format) and increase the type number to the next available on until the type number reaches over 65535 which is the max number for the 16 bit type. After it reaches that number, the logic to allocate a new number simply looks for the next available number. When an dynamic event is removed, that number is then available to be reused by the next dynamic event created. That is, once the above reaches the max number, the number assigned to the event in that loop will remain the same.
Now that means deleting one dynamic event and created another will reuse the previous events type number. This is where bad things can happen. After the above loop finishes, the kprobes/foo event which reads the do_sys_openat2 function call's first parameter as an integer.
Now if we delete the kprobe and create a new one that reads a string:
# echo 'p:kprobes/foo do_sys_openat2 +0($arg2):string' > kprobe_events
And now we can the trace:
Detalles técnicos trazas, registros y código del informe original
# echo 1 > kprobes/foo/enable
# cat /etc/passwd > /dev/null
# cat trace
cat-2211 [005] .... 2007.849603: foo: (do_sys_openat2+0x0/0x130) arg1=4294967196
cat-2211 [005] .... 2007.849620: foo: (do_sys_openat2+0x0/0x130) arg1=4294967196
cat-2211 [005] .... 2007.849838: foo: (do_sys_openat2+0x0/0x130) arg1=4294967196
cat-2211 [005] .... 2007.849880: foo: (do_sys_openat2+0x0/0x130) arg1=4294967196
# echo 0 > kprobes/foo/enable
# cat trace
sendmail-1942 [002] ..... 530.136320: foo: (do_sys_openat2+0x0/0x240) arg1= cat-2046 [004] ..... 530.930817: foo: (do_sys_openat2+0x0/0x240) arg1="������������������������������������������������������������������������������������������������"
cat-2046 [004] ..... 530.930961: foo: (do_sys_openat2+0x0/0x240) arg1="������������������������������������������������������������������������������������������������"
cat-2046 [004] ..... 530.934278: foo: (do_sys_openat2+0x0/0x240) arg1="������������������������������������������������������������������������������������������������"
cat-2046 [004] ..... 530.934563: foo: (do_sys_openat2+0x0/0x240) arg1="���������������������������������������
---truncated---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: 0.26%
- Percentil entre todas las CVEs puntuadas: 16
- 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
T1068Exploitation for Privilege Escalationprivilege escalation85 % - Impacto principal
T1059Command and Scripting Interpreterexecution75 % - Impacto secundario
T1499.004Application or System Exploitationimpact70 %
Vulnerabilidad de use-after-free (CWE-416) en kernel de Linux con acceso local sin interacción (AV:L/PR:L/UI:N). Permite escalada de privilegios reutilizando números de tipo de eventos dinámicos para ejecutar código o causar DoS por corrupción de memoria en el ring buffer de tracing.
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
Tecnologías afectadas (1)
CWE
- CWE-416
Referencias
- https://git.kernel.org/stable/c/1603feac154ff38514e8354e3079a455eb4801e2
- https://git.kernel.org/stable/c/417d5ea6e735e5d88ffb6c436cf2938f3f476dd1
- https://git.kernel.org/stable/c/4313e5a613049dfc1819a6dfb5f94cf2caff9452
- https://git.kernel.org/stable/c/be111ebd8868d4b7c041cb3c6102e1ae27d6dc1d
- https://git.kernel.org/stable/c/c52d0c8c4f38f7580cff61c4dfe1034c580cedfd
JSON original (NVD)
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"value": "In the Linux kernel, the following vulnerability has been resolved:\n\ntracing: Free buffers when a used dynamic event is removed\n\nAfter 65536 dynamic events have been added and removed, the \"type\" field\nof the event then uses the first type number that is available (not\ncurrently used by other events). A type number is the identifier of the\nbinary blobs in the tracing ring buffer (known as events) to map them to\nlogic that can parse the binary blob.\n\nThe issue is that if a dynamic event (like a kprobe event) is traced and\nis in the ring buffer, and then that event is removed (because it is\ndynamic, which means it can be created and destroyed), if another dynamic\nevent is created that has the same number that new event's logic on\nparsing the binary blob will be used.\n\nTo show how this can be an issue, the following can crash the kernel:\n\n # cd /sys/kernel/tracing\n # for i in `seq 65536`; do\n echo 'p:kprobes/foo do_sys_openat2 $arg1:u32' > kprobe_events\n # done\n\nFor every iteration of the above, the writing to the kprobe_events will\nremove the old event and create a new one (with the same format) and\nincrease the type number to the next available on until the type number\nreaches over 65535 which is the max number for the 16 bit type. After it\nreaches that number, the logic to allocate a new number simply looks for\nthe next available number. When an dynamic event is removed, that number\nis then available to be reused by the next dynamic event created. That is,\nonce the above reaches the max number, the number assigned to the event in\nthat loop will remain the same.\n\nNow that means deleting one dynamic event and created another will reuse\nthe previous events type number. This is where bad things can happen.\nAfter the above loop finishes, the kprobes/foo event which reads the\ndo_sys_openat2 function call's first parameter as an integer.\n\n # echo 1 > kprobes/foo/enable\n # cat /etc/passwd > /dev/null\n # cat trace\n cat-2211 [005] .... 2007.849603: foo: (do_sys_openat2+0x0/0x130) arg1=4294967196\n cat-2211 [005] .... 2007.849620: foo: (do_sys_openat2+0x0/0x130) arg1=4294967196\n cat-2211 [005] .... 2007.849838: foo: (do_sys_openat2+0x0/0x130) arg1=4294967196\n cat-2211 [005] .... 2007.849880: foo: (do_sys_openat2+0x0/0x130) arg1=4294967196\n # echo 0 > kprobes/foo/enable\n\nNow if we delete the kprobe and create a new one that reads a string:\n\n # echo 'p:kprobes/foo do_sys_openat2 +0($arg2):string' > kprobe_events\n\nAnd now we can the trace:\n\n # cat trace\n sendmail-1942 [002] ..... 530.136320: foo: (do_sys_openat2+0x0/0x240) arg1= cat-2046 [004] ..... 530.930817: foo: (do_sys_openat2+0x0/0x240) arg1=\"������������������������������������������������������������������������������������������������\"\n cat-2046 [004] ..... 530.930961: foo: (do_sys_openat2+0x0/0x240) arg1=\"������������������������������������������������������������������������������������������������\"\n cat-2046 [004] ..... 530.934278: foo: (do_sys_openat2+0x0/0x240) arg1=\"������������������������������������������������������������������������������������������������\"\n cat-2046 [004] ..... 530.934563: foo: (do_sys_openat2+0x0/0x240) arg1=\"���������������������������������������\n---truncated---"
},
{
"lang": "es",
"value": "En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: rastreo: Búferes libres cuando se elimina un evento dinámico usado Después de que se hayan agregado y eliminado 65536 eventos dinámicos, el campo \"tipo\" del evento usa el primer número de tipo que está disponible (no usado actualmente por otros eventos). Un número de tipo es el identificador de los blobs binarios en el búfer de anillo de rastreo (conocidos como eventos) para mapearlos a la lógica que puede analizar el blob binario. El problema es que si se rastrea un evento dinámico (como un evento kprobe) y está en el búfer de anillo, y luego ese evento se elimina (porque es dinámico, lo que significa que se puede crear y destruir), si se crea otro evento dinámico que tenga el mismo número, se usará la lógica de ese nuevo evento al analizar el blob binario. Para mostrar cómo esto puede ser un problema, lo siguiente puede bloquear el kernel: # cd /sys/kernel/tracing # for i in `seq 65536`; Para cada iteración de lo anterior, la escritura en kprobe_events eliminará el evento anterior y creará uno nuevo (con el mismo formato) y aumentará el número de tipo al siguiente disponible hasta que el número de tipo alcance más de 65535, que es el número máximo para el tipo de 16 bits. Después de que alcanza ese número, la lógica para asignar un nuevo número simplemente busca el siguiente número disponible. Cuando se elimina un evento dinámico, ese número está disponible para ser reutilizado por el próximo evento dinámico creado. Es decir, una vez que lo anterior alcanza el número máximo, el número asignado al evento en ese bucle seguirá siendo el mismo. Ahora, eso significa que eliminar un evento dinámico y crear otro reutilizará el número de tipo de eventos anteriores. Aquí es donde pueden suceder cosas malas. Después de que finaliza el bucle anterior, el evento kprobes/foo que lee el primer parámetro de la llamada a la función do_sys_openat2 como un entero. # echo 1 > kprobes/foo/enable # cat /etc/passwd > /dev/null # cat seguimiento cat-2211 [005] .... 2007.849603: foo: (do_sys_openat2+0x0/0x130) arg1=4294967196 cat-2211 [005] .... 2007.849620: foo: (do_sys_openat2+0x0/0x130) arg1=4294967196 cat-2211 [005] .... 2007.849838: foo: (do_sys_openat2+0x0/0x130) arg1=4294967196 cat-2211 [005] .... 2007.849880: foo: (do_sys_openat2+0x0/0x130) arg1=4294967196 # echo 0 > kprobes/foo/enable Ahora si borramos el kprobe y creamos uno nuevo que lea una cadena: # echo 'p:kprobes/foo do_sys_openat2 +0($arg2):string' > kprobe_events Y ahora podemos hacer el trace: # cat trace sendmail-1942 [002] ..... 530.136320: foo: (do_sys_openat2+0x0/0x240) arg1= cat-2046 [004] ..... 530.930817: foo: (do_sys_openat2+0x0/0x240) arg1=\"????????????????????????????????????????????? ????????????????????????????????????????????????????????????????\" cat-2046 [004] ..... 530.930961: foo: (do_sys_openat2+0x0/0x240) arg1=\"????????????????????????????????????????????? ??????????????????????????????????????????????????????????????????\" cat-2046 [004] ..... 530.934278: foo: (do_sys_openat2+0x0/0x240) arg1=\"????????????????????????????????????????????? ??????????????????????????????????????????????????\" cat-2046 [004] ..... 530.934563: foo: (do_sys_openat2+0x0/0x240) arg1=\"????????????????????????????????????????? ---truncado---"
}
],
"lastModified": "2026-06-17T05:16:49.920",
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