CVE-2024-56558

Estado: ModificadaAlta (7.8)—

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

nfsd: make sure exp active before svc_export_show

The function `e_show` was called with protection from RCU. This only ensures that `exp` will not be freed. Therefore, the reference count for `exp` can drop to zero, which will trigger a refcount use-after-free warning when `exp_get` is called. To resolve this issue, use `cache_get_rcu` to ensure that `exp` remains active.

Detalles técnicos trazas, registros y código del informe original

------------[ cut here ]------------
refcount_t: addition on 0; use-after-free.
WARNING: CPU: 3 PID: 819 at lib/refcount.c:25
refcount_warn_saturate+0xb1/0x120
CPU: 3 UID: 0 PID: 819 Comm: cat Not tainted 6.12.0-rc3+ #1
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
1.16.1-2.fc37 04/01/2014
RIP: 0010:refcount_warn_saturate+0xb1/0x120
...
Call Trace:
 <TASK>
 e_show+0x20b/0x230 [nfsd]
 seq_read_iter+0x589/0x770
 seq_read+0x1e5/0x270
 vfs_read+0x125/0x530
 ksys_read+0xc1/0x160
 do_syscall_64+0x5f/0x170
 entry_SYSCALL_64_after_hwframe+0x76/0x7e

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 principalT1499.004 Application or System Exploitationimpact75 %

Vulnerabilidad local (AV:L/PR:L) que causa uso-después-liberación (CWE-416) en el kernel Linux; puede llevar a DoS por corrupción de memoria con acceso local privilegiado.

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 Filter Network Traffic Execution Prevention Application Isolation and Sandboxing Exploit Protection Update Software

Tecnologías afectadas (1)

Linux — Linux Kernel

CWE

CWE-416

Referencias

JSON original (NVD)

Mostrar

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      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnfsd: make sure exp active before svc_export_show\n\nThe function `e_show` was called with protection from RCU. This only\nensures that `exp` will not be freed. Therefore, the reference count for\n`exp` can drop to zero, which will trigger a refcount use-after-free\nwarning when `exp_get` is called. To resolve this issue, use\n`cache_get_rcu` to ensure that `exp` remains active.\n\n------------[ cut here ]------------\nrefcount_t: addition on 0; use-after-free.\nWARNING: CPU: 3 PID: 819 at lib/refcount.c:25\nrefcount_warn_saturate+0xb1/0x120\nCPU: 3 UID: 0 PID: 819 Comm: cat Not tainted 6.12.0-rc3+ #1\nHardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS\n1.16.1-2.fc37 04/01/2014\nRIP: 0010:refcount_warn_saturate+0xb1/0x120\n...\nCall Trace:\n <TASK>\n e_show+0x20b/0x230 [nfsd]\n seq_read_iter+0x589/0x770\n seq_read+0x1e5/0x270\n vfs_read+0x125/0x530\n ksys_read+0xc1/0x160\n do_syscall_64+0x5f/0x170\n entry_SYSCALL_64_after_hwframe+0x76/0x7e"
    },
    {
      "lang": "es",
      "value": "En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: nfsd: asegúrese de que exp esté activo antes de svc_export_show La función `e_show` se llamó con protección de RCU. Esto solo garantiza que `exp` no se liberará. Por lo tanto, el recuento de referencia para `exp` puede caer a cero, lo que activará una advertencia de use-after-free de refcount cuando se llame a `exp_get`. Para resolver este problema, use `cache_get_rcu` para asegurarse de que `exp` permanezca activo. ------------[ cortar aquí ]------------ refcount_t: adición en 0; use-after-free. ADVERTENCIA: CPU: 3 PID: 819 en lib/refcount.c:25 refcount_warn_saturate+0xb1/0x120 CPU: 3 UID: 0 PID: 819 Comm: cat No contaminado 6.12.0-rc3+ #1 Nombre del hardware: PC estándar QEMU (i440FX + PIIX, 1996), BIOS 1.16.1-2.fc37 01/04/2014 RIP: 0010:refcount_warn_saturate+0xb1/0x120 ... Seguimiento de llamadas:  e_show+0x20b/0x230 [nfsd] seq_read_iter+0x589/0x770 seq_read+0x1e5/0x270 vfs_read+0x125/0x530 ksys_read+0xc1/0x160 hacer_syscall_64+0x5f/0x170 entrada_SYSCALL_64_después_hwframe+0x76/0x7e"
    }
  ],
  "lastModified": "2026-06-17T08:12:23.337",
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