CVE-2026-53399

Estado: AnalizadaCrítica (9.8)—

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

nfsd: release layout stid on setlease failure

nfs4_alloc_stid() publishes the new stid into cl->cl_stateids via idr_alloc_cyclic() under cl_lock before returning to nfsd4_alloc_layout_stateid(). When nfsd4_layout_setlease() then fails, the error path frees the layout stateid directly with kmem_cache_free() without ever calling idr_remove(), leaving the IDR slot pointing at freed slab memory. Any subsequent IDR walker (states_show, client teardown) dereferences the dangling pointer.

The correct teardown for an IDR-published stid is nfs4_put_stid(), which removes the IDR slot under cl_lock, dispatches sc_free (nfsd4_free_layout_stateid) to release ls->ls_file via nfsd4_close_layout(), and drops the nfs4_file reference in its tail.

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A second issue blocks that switch: nfsd4_free_layout_stateid() unconditionally inspects ls->ls_fence_work via delayed_work_pending() under ls_lock, but INIT_DELAYED_WORK(&ls->ls_fence_work, ...) currently runs only after the setlease call. On the setlease-failure path the destructor would touch an uninitialized delayed_work.

Fix by hoisting the ls_fenced / ls_fence_delay / INIT_DELAYED_WORK initialization above the nfsd4_layout_setlease() call, and replace the manual nfsd_file_put + put_nfs4_file + kmem_cache_free cleanup with a single nfs4_put_stid(stp).

Detalles técnicos trazas, registros y código del informe original

    nfsd4_alloc_layout_stateid()
      nfs4_alloc_stid()           /* idr_alloc_cyclic under cl_lock */
      nfsd4_layout_setlease()     /* fails */
        nfs4_put_stid()
          nfsd4_free_layout_stateid()
            delayed_work_pending(&ls->ls_fence_work)  /* needs INIT */
            nfsd4_close_layout()  /* nfsd_file_put(ls->ls_file) */
          put_nfs4_file()

CVSS

Versión: 3.1
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Puntuación base: 9.8

Probabilidad de explotación (EPSS)

Probabilidad de explotación en los próximos 30 días: 0.54%
Percentil entre todas las CVEs puntuadas: 44
Fecha de la puntuación: 3/10/2026

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.

ExplotaciónT1190 Exploit Public-Facing Applicationinitial access75 %

Vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N indica explotación remota sin privilegios previos. Fallo en gestión de memoria (CWE-476: null pointer dereference) en kernel NFSv4 permite DoS por dereferencia de puntero colgante. Escalada potencial por corrupción de memoria.

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 Scanning Privileged Account Management Network Segmentation Limit Access to Resource Over Network Filter Network Traffic Application Isolation and Sandboxing

Tecnologías afectadas (1)

Linux — Linux Kernel

CWE

CWE-476

Referencias

JSON original (NVD)

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      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnfsd: release layout stid on setlease failure\n\nnfs4_alloc_stid() publishes the new stid into cl->cl_stateids via\nidr_alloc_cyclic() under cl_lock before returning to\nnfsd4_alloc_layout_stateid(). When nfsd4_layout_setlease() then\nfails, the error path frees the layout stateid directly with\nkmem_cache_free() without ever calling idr_remove(), leaving the\nIDR slot pointing at freed slab memory. Any subsequent IDR walker\n(states_show, client teardown) dereferences the dangling pointer.\n\nThe correct teardown for an IDR-published stid is nfs4_put_stid(),\nwhich removes the IDR slot under cl_lock, dispatches sc_free\n(nfsd4_free_layout_stateid) to release ls->ls_file via\nnfsd4_close_layout(), and drops the nfs4_file reference in its\ntail.\n\nA second issue blocks that switch: nfsd4_free_layout_stateid()\nunconditionally inspects ls->ls_fence_work via\ndelayed_work_pending() under ls_lock, but\nINIT_DELAYED_WORK(&ls->ls_fence_work, ...) currently runs only\nafter the setlease call. On the setlease-failure path the\ndestructor would touch an uninitialized delayed_work.\n\n    nfsd4_alloc_layout_stateid()\n      nfs4_alloc_stid()           /* idr_alloc_cyclic under cl_lock */\n      nfsd4_layout_setlease()     /* fails */\n        nfs4_put_stid()\n          nfsd4_free_layout_stateid()\n            delayed_work_pending(&ls->ls_fence_work)  /* needs INIT */\n            nfsd4_close_layout()  /* nfsd_file_put(ls->ls_file) */\n          put_nfs4_file()\n\nFix by hoisting the ls_fenced / ls_fence_delay / INIT_DELAYED_WORK\ninitialization above the nfsd4_layout_setlease() call, and replace\nthe manual nfsd_file_put + put_nfs4_file + kmem_cache_free cleanup\nwith a single nfs4_put_stid(stp)."
    }
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