CVE-2025-37953
Estado: AnalizadaMedia (5.5)—
In the Linux kernel, the following vulnerability has been resolved:
sch_htb: make htb_deactivate() idempotent
Alan reported a NULL pointer dereference in htb_next_rb_node() after we made htb_qlen_notify() idempotent.
It turns out in the following case it introduced some regression:
For htb_next_rb_node(), after calling the 1st htb_deactivate(), the clprio[prio]->ptr could be already set to NULL, which means htb_next_rb_node() is vulnerable here.
For htb_deactivate(), although we checked qlen before calling it, in case of qlen==0 after qdisc_tree_reduce_backlog(), we may call it again which triggers the warning inside.
Leer descripción completaMostrar menos
To fix the issues here, we need to:
1) Make htb_deactivate() idempotent, that is, simply return if we already call it before. 2) Make htb_next_rb_node() safe against ptr==NULL.
Many thanks to Alan for testing and for the reproducer.
Detalles técnicos trazas, registros y código del informe original
htb_dequeue_tree():
|-> fq_codel_dequeue()
|-> qdisc_tree_reduce_backlog()
|-> htb_qlen_notify()
|-> htb_deactivate()
|-> htb_next_rb_node()
|-> htb_deactivate()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: 0.19%
- Percentil entre todas las CVEs puntuadas: 7
- 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 (2)
CWE
- CWE-476
Referencias
- https://git.kernel.org/stable/c/31ff70ad39485698cf779f2078132d80b57f6c07
- https://git.kernel.org/stable/c/3769478610135e82b262640252d90f6efb05be71
- https://git.kernel.org/stable/c/98cd7ed92753090a714f0802d4434314526fe61d
- https://git.kernel.org/stable/c/99ff8a20fd61315bf9ae627440a5ff07d22ee153
- https://git.kernel.org/stable/c/a9945f7cf1709adc5d2d31cb6cfc85627ce299a8
- https://git.kernel.org/stable/c/c2d25fddd867ce20a266806634eeeb5c30cb520c
- https://git.kernel.org/stable/c/c4792b9e38d2f61b07eac72f10909fa76130314b
- https://git.kernel.org/stable/c/c928dd4f6bf0c25c72b11824a1e9ac9bd37296a0
- https://lists.debian.org/debian-lts-announce/2025/08/msg00010.html
JSON original (NVD)
Mostrar
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"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsch_htb: make htb_deactivate() idempotent\n\nAlan reported a NULL pointer dereference in htb_next_rb_node()\nafter we made htb_qlen_notify() idempotent.\n\nIt turns out in the following case it introduced some regression:\n\nhtb_dequeue_tree():\n |-> fq_codel_dequeue()\n |-> qdisc_tree_reduce_backlog()\n |-> htb_qlen_notify()\n |-> htb_deactivate()\n |-> htb_next_rb_node()\n |-> htb_deactivate()\n\nFor htb_next_rb_node(), after calling the 1st htb_deactivate(), the\nclprio[prio]->ptr could be already set to NULL, which means\nhtb_next_rb_node() is vulnerable here.\n\nFor htb_deactivate(), although we checked qlen before calling it, in\ncase of qlen==0 after qdisc_tree_reduce_backlog(), we may call it again\nwhich triggers the warning inside.\n\nTo fix the issues here, we need to:\n\n1) Make htb_deactivate() idempotent, that is, simply return if we\n already call it before.\n2) Make htb_next_rb_node() safe against ptr==NULL.\n\nMany thanks to Alan for testing and for the reproducer."
},
{
"lang": "es",
"value": "En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: sch_htb: hacer que htb_deactivate() sea idempotente. Alan informó una desreferencia de puntero NULL en htb_next_rb_node() después de que htb_qlen_notify() fuera idempotente. Resulta que en el siguiente caso introdujo alguna regresión: htb_dequeue_tree(): |-> fq_codel_dequeue() |-> qdisc_tree_reduce_backlog() |-> htb_qlen_notify() |-> htb_deactivate() |-> htb_next_rb_node() |-> htb_deactivate() Para htb_next_rb_node(), después de llamar al primer htb_deactivate(), el clprio[prio]->ptr podría estar ya establecido en NULL, lo que significa que htb_next_rb_node() es vulnerable aquí. Para htb_deactivate(), aunque verificamos qlen antes de llamarlo, en caso de qlen==0 después de qdisc_tree_reduce_backlog(), podemos llamarlo nuevamente, lo que activa la advertencia interna. Para solucionar estos problemas, necesitamos: 1) Hacer que htb_deactivate() sea idempotente, es decir, que simplemente regrese si ya lo llamamos. 2) Hacer que htb_next_rb_node() sea seguro contra ptr==NULL. Muchas gracias a Alan por las pruebas y por el reproductor."
}
],
"lastModified": "2026-06-17T09:15:45.963",
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