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CVE-2026-31718

Estado: ModificadaCrítica (9.8)—

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

ksmbd: fix use-after-free in __ksmbd_close_fd() via durable scavenger

When a durable file handle survives session disconnect (TCP close without SMB2_LOGOFF), session_fd_check() sets fp->conn = NULL to preserve the handle for later reconnection. However, it did not clean up the byte-range locks on fp->lock_list.

Later, when the durable scavenger thread times out and calls __ksmbd_close_fd(NULL, fp), the lock cleanup loop did:

This caused a slab use-after-free because fp->conn was NULL and the original connection object had already been freed by ksmbd_tcp_disconnect().

Leer descripción completaMostrar menos

The root cause is asymmetric cleanup: lock entries (smb_lock->clist) were left dangling on the freed conn->lock_list while fp->conn was nulled out.

To fix this issue properly, we need to handle the lifetime of smb_lock->clist across three paths: - Safely skip clist deletion when list is empty and fp->conn is NULL. - Remove the lock from the old connection's lock_list in session_fd_check() - Re-add the lock to the new connection's lock_list in ksmbd_reopen_durable_fd().

Detalles técnicos trazas, registros y código del informe original
    spin_lock(&fp->conn->llist_lock);

CVSS

Probabilidad de explotación (EPSS)

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.

Vector CVSS AV:N/AC:L/PR:N indica red sin autenticación (T1190). Use-after-free en kernel ksmbd permite ejecución de código remoto; impacto T1059 por potencial RCE, aunque el texto no describe explícitamente command execution.

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

Vulnerability ScanningPrivileged Account ManagementNetwork SegmentationLimit Access to Resource Over NetworkFilter Network TrafficApplication Isolation and Sandboxing

Tecnologías afectadas (1)

Linux — Linux Kernel

CWE

Referencias

JSON original (NVD)

Mostrar
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      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: fix use-after-free in __ksmbd_close_fd() via durable scavenger\n\nWhen a durable file handle survives session disconnect (TCP close without\nSMB2_LOGOFF), session_fd_check() sets fp->conn = NULL to preserve the\nhandle for later reconnection. However, it did not clean up the byte-range\nlocks on fp->lock_list.\n\nLater, when the durable scavenger thread times out and calls\n__ksmbd_close_fd(NULL, fp), the lock cleanup loop did:\n\n    spin_lock(&fp->conn->llist_lock);\n\nThis caused a slab use-after-free because fp->conn was NULL and the\noriginal connection object had already been freed by\nksmbd_tcp_disconnect().\n\nThe root cause is asymmetric cleanup: lock entries (smb_lock->clist) were\nleft dangling on the freed conn->lock_list while fp->conn was nulled out.\n\nTo fix this issue properly, we need to handle the lifetime of\nsmb_lock->clist across three paths:\n - Safely skip clist deletion when list is empty and fp->conn is NULL.\n - Remove the lock from the old connection's lock_list in\n   session_fd_check()\n - Re-add the lock to the new connection's lock_list in\n   ksmbd_reopen_durable_fd()."
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