CVE-2026-63804

Estado: AnalizadaAlta (7.8)—

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

gfs2: fix use-after-free in gfs2_qd_dealloc

gfs2_qd_dealloc(), called as an RCU callback from gfs2_qd_dispose(), accesses the superblock object sdp through qd->qd_sbd after freeing qd. It does so to decrement sd_quota_count and wake up sd_kill_wait.

However, by the time the RCU callback runs, gfs2_put_super() may have already freed sdp via free_sbd(). This can happen when gfs2_quota_cleanup() is called during unmount: it disposes of quota objects via call_rcu() and then waits on sd_kill_wait with a 60-second timeout.

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If the timeout expires, or if gfs2_gl_hash_clear() triggers additional qd_put() calls that schedule more RCU callbacks after the wait completes, gfs2_put_super() will proceed to free the superblock while RCU callbacks referencing it are still pending.

Add an rcu_barrier() before free_sbd() in gfs2_put_super() to ensure all pending RCU callbacks (including gfs2_qd_dealloc) have completed before the superblock is freed.

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: 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.

ExplotaciónT1068 Exploitation for Privilege Escalationprivilege escalation75 %

Vulnerabilidad de use-after-free (CWE-416) en kernel Linux con acceso local y permisos requeridos (PR:L). Permite ejecución de código al liberar memoria que aún se referencia, típico de escalada de privilegios local.

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

Threat Intelligence Program Execution Prevention Application Isolation and Sandboxing Exploit Protection Update Software

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\ngfs2: fix use-after-free in gfs2_qd_dealloc\n\ngfs2_qd_dealloc(), called as an RCU callback from gfs2_qd_dispose(),\naccesses the superblock object sdp through qd->qd_sbd after freeing qd.\nIt does so to decrement sd_quota_count and wake up sd_kill_wait.\n\nHowever, by the time the RCU callback runs, gfs2_put_super() may have\nalready freed sdp via free_sbd().  This can happen when\ngfs2_quota_cleanup() is called during unmount: it disposes of quota\nobjects via call_rcu() and then waits on sd_kill_wait with a 60-second\ntimeout.  If the timeout expires, or if gfs2_gl_hash_clear() triggers\nadditional qd_put() calls that schedule more RCU callbacks after the\nwait completes, gfs2_put_super() will proceed to free the superblock\nwhile RCU callbacks referencing it are still pending.\n\nAdd an rcu_barrier() before free_sbd() in gfs2_put_super() to ensure\nall pending RCU callbacks (including gfs2_qd_dealloc) have completed\nbefore the superblock is freed."
    }
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