CVE-2025-71159

Estado: ModificadaAlta (7.8)—

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

btrfs: fix use-after-free warning in btrfs_get_or_create_delayed_node()

Previously, btrfs_get_or_create_delayed_node() set the delayed_node's refcount before acquiring the root->delayed_nodes lock. Commit e8513c012de7 ("btrfs: implement ref_tracker for delayed_nodes") moved refcount_set inside the critical section, which means there is no longer a memory barrier between setting the refcount and setting btrfs_inode->delayed_node.

Without that barrier, the stores to node->refs and btrfs_inode->delayed_node may become visible out of order.

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Another thread can then read btrfs_inode->delayed_node and attempt to increment a refcount that hasn't been set yet, leading to a refcounting bug and a use-after-free warning.

The fix is to move refcount_set back to where it was to take advantage of the implicit memory barrier provided by lock acquisition.

Because the allocations now happen outside of the lock's critical section, they can use GFP_NOFS instead of GFP_ATOMIC.

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: 0.24%
Percentil entre todas las CVEs puntuadas: 14
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 Interpreterexecution70 %

CWE-416 (use-after-free) en kernel Linux con AV:L/PR:L permite escalada local; el impacto potencial es ejecución de código mediante explotación de la condición de carrera de refcounting.

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 Behavior Prevention on Endpoint

Tecnologías afectadas (1)

Linux — Linux Kernel

CWE

CWE-416

Referencias

JSON original (NVD)

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      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbtrfs: fix use-after-free warning in btrfs_get_or_create_delayed_node()\n\nPreviously, btrfs_get_or_create_delayed_node() set the delayed_node's\nrefcount before acquiring the root->delayed_nodes lock.\nCommit e8513c012de7 (\"btrfs: implement ref_tracker for delayed_nodes\")\nmoved refcount_set inside the critical section, which means there is\nno longer a memory barrier between setting the refcount and setting\nbtrfs_inode->delayed_node.\n\nWithout that barrier, the stores to node->refs and\nbtrfs_inode->delayed_node may become visible out of order. Another\nthread can then read btrfs_inode->delayed_node and attempt to\nincrement a refcount that hasn't been set yet, leading to a\nrefcounting bug and a use-after-free warning.\n\nThe fix is to move refcount_set back to where it was to take\nadvantage of the implicit memory barrier provided by lock\nacquisition.\n\nBecause the allocations now happen outside of the lock's critical\nsection, they can use GFP_NOFS instead of GFP_ATOMIC."
    },
    {
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      "value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\nbtrfs: soluciona la advertencia de uso después de liberación en btrfs_get_or_create_delayed_node()\n\nAnteriormente, btrfs_get_or_create_delayed_node() establecía el refcount del delayed_node antes de adquirir el bloqueo root-&gt;delayed_nodes. El commit e8513c012de7 ('btrfs: implementa ref_tracker para delayed_nodes') movió refcount_set dentro de la sección crítica, lo que significa que ya no hay una barrera de memoria entre el establecimiento del refcount y el establecimiento de btrfs_inode-&gt;delayed_node.\n\nSin esa barrera, los almacenamientos en node-&gt;refs y btrfs_inode-&gt;delayed_node pueden volverse visibles fuera de orden. Otro hilo puede entonces leer btrfs_inode-&gt;delayed_node e intentar incrementar un refcount que aún no ha sido establecido, lo que lleva a un error de refcounting y a una advertencia de uso después de liberación.\n\nLa solución es mover refcount_set de vuelta a donde estaba para aprovechar la barrera de memoria implícita proporcionada por la adquisición del bloqueo.\n\nDebido a que las asignaciones ahora ocurren fuera de la sección crítica del bloqueo, pueden usar GFP_NOFS en lugar de GFP_ATOMIC."
    }
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  "lastModified": "2026-07-30T06:24:54.993",
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