CVE-2025-21731
Estado: ModificadaAlta (7.8)—
In the Linux kernel, the following vulnerability has been resolved:
nbd: don't allow reconnect after disconnect
Following process can cause nbd_config UAF:
2) nbd_genl_disconnect() flush all recv_work() and release the initial reference:
5) Finially, recv_work() will trigger UAF:
Fix the problem by clearing NBD_RT_BOUND in nbd_genl_disconnect(), so that nbd_genl_reconfigure() will fail.
Detalles técnicos trazas, registros y código del informe original
1) grab nbd_config temporarily;
nbd_genl_disconnect
nbd_disconnect_and_put
nbd_disconnect
flush_workqueue(nbd->recv_workq)
if (test_and_clear_bit(NBD_RT_HAS_CONFIG_REF, ...))
nbd_config_put
-> due to step 1), reference is still not zero
3) nbd_genl_reconfigure() queue recv_work() again;
nbd_genl_reconfigure
config = nbd_get_config_unlocked(nbd)
if (!config)
-> succeed
if (!test_bit(NBD_RT_BOUND, ...))
-> succeed
nbd_reconnect_socket
queue_work(nbd->recv_workq, &args->work)
4) step 1) release the reference;
recv_work
nbd_config_put(nbd)
-> nbd_config is freed
atomic_dec(&config->recv_threads)
-> UAFCVSS
- 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: 0.23%
- Percentil entre todas las CVEs puntuadas: 13
- 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 Interpreterexecution70 %
Vulnerabilidad de UAF (CWE-416) en kernel Linux que requiere acceso local con privilegios (AV:L, PR:L). Permite ejecución de código mediante aprovechamiento de condición de carrera en nbd_genl_reconfigure().
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/6bef6222a3f6c7adb6396f77f25a3579d821b09a
- https://git.kernel.org/stable/c/844b8cdc681612ff24df62cdefddeab5772fadf1
- https://git.kernel.org/stable/c/9793bd5ae4bdbdb2dde401a3cab94a6bfd05e302
- https://git.kernel.org/stable/c/a8ee6ecde2b7bfb58c8a3afe8a9d2b848f580739
- https://git.kernel.org/stable/c/d208d2c52b652913b5eefc8ca434b0d6b757f68f
- https://git.kernel.org/stable/c/e3be8862d73cac833e0fb7602636c19c6cb94b11
- https://git.kernel.org/stable/c/e70a578487a47d7cf058904141e586684d1c3381
- https://git.kernel.org/stable/c/e7343fa33751cb07c1c56b666bf37cfca357130e
- https://lists.debian.org/debian-lts-announce/2025/03/msg00028.html
- https://lists.debian.org/debian-lts-announce/2025/05/msg00030.html
- https://cert-portal.siemens.com/productcert/html/ssa-019113.html
JSON original (NVD)
Mostrar
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"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnbd: don't allow reconnect after disconnect\n\nFollowing process can cause nbd_config UAF:\n\n1) grab nbd_config temporarily;\n\n2) nbd_genl_disconnect() flush all recv_work() and release the\ninitial reference:\n\n nbd_genl_disconnect\n nbd_disconnect_and_put\n nbd_disconnect\n flush_workqueue(nbd->recv_workq)\n if (test_and_clear_bit(NBD_RT_HAS_CONFIG_REF, ...))\n nbd_config_put\n -> due to step 1), reference is still not zero\n\n3) nbd_genl_reconfigure() queue recv_work() again;\n\n nbd_genl_reconfigure\n config = nbd_get_config_unlocked(nbd)\n if (!config)\n -> succeed\n if (!test_bit(NBD_RT_BOUND, ...))\n -> succeed\n nbd_reconnect_socket\n queue_work(nbd->recv_workq, &args->work)\n\n4) step 1) release the reference;\n\n5) Finially, recv_work() will trigger UAF:\n\n recv_work\n nbd_config_put(nbd)\n -> nbd_config is freed\n atomic_dec(&config->recv_threads)\n -> UAF\n\nFix the problem by clearing NBD_RT_BOUND in nbd_genl_disconnect(), so\nthat nbd_genl_reconfigure() will fail."
},
{
"lang": "es",
"value": "En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: nbd: no permitir la reconexión después de la desconexión El siguiente proceso puede causar el nbd_config UAF: 1) grab nbd_config temporarily; 2) nbd_genl_disconnect() flush all recv_work() and release the initial reference: nbd_genl_disconnect nbd_disconnect_and_put nbd_disconnect flush_workqueue(nbd->recv_workq) if (test_and_clear_bit(NBD_RT_HAS_CONFIG_REF, ...)) nbd_config_put -> due to step 1), reference is still not zero 3) nbd_genl_reconfigure() queue recv_work() again; nbd_genl_reconfigure config = nbd_get_config_unlocked(nbd) if (!config) -> succeed if (!test_bit(NBD_RT_BOUND, ...)) -> succeed nbd_reconnect_socket queue_work(nbd->recv_workq, &args->work) 4) step 1) release the reference; 5) Finially, recv_work() will trigger UAF: recv_work nbd_config_put(nbd) -> nbd_config is freed atomic_dec(&config->recv_threads) -> UAF Fix the problem by clearing NBD_RT_BOUND in nbd_genl_disconnect(), so that nbd_genl_reconfigure() will fail. "
}
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"lastModified": "2026-07-14T13:17:22.003",
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