CVE-2026-72323

Estado: RecibidaCrítica (9.8)—

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

ipv4: igmp: Fix potential UAF in igmp_gq_start_timer()

A race condition exists between device teardown (inetdev_destroy) and incoming IGMP query processing (igmp_rcv), leading to a Use-After-Free in the IGMP timer callback.

During device destruction, inetdev_destroy() drops the primary reference to in_device, which can drop its refcount to 0. The actual freeing of in_device memory is deferred via RCU (using call_rcu()).

Concurrently, igmp_rcv() runs under RCU read lock and obtains the in_device pointer. Because the memory is RCU-protected, CPU-0 can safely dereference in_device even if its refcount has hit 0.

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However, if CPU-0 calls igmp_gq_start_timer() and re-arms the timer, it attempts to acquire a reference using in_dev_hold(). This increments the refcount from 0 to 1, triggering a "refcount_t: addition on 0" warning. Since the in_device memory is still scheduled to be freed after the RCU grace period (as the free callback does not check the refcount again), the device is freed while the timer is still armed. When the timer expires, it accesses the freed memory, causing a kernel panic.

Fix this by using refcount_inc_not_zero() (via a new helper in_dev_hold_safe()) to prevent acquiring a reference if the device is already being destroyed. If the refcount is 0, we do not arm the timer.

A similar issue in IPv6 MLD is fixed in a subsequent patch.

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: 0.72%
Percentil entre todas las CVEs puntuadas: 53
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.

ExplotaciónT1190 Exploit Public-Facing Applicationinitial access75 %
Impacto principalT1499.004 Application or System Exploitationimpact85 %

Vulnerabilidad de red remota sin autenticación (AV:N/PR:N/UI:N) que causa panic en kernel por UAF; explotable via IGMP queries para DoS o escalada de privilegios.

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

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

Tecnologías afectadas (1)

⚠ Inferidas por IA a partir de la descripción — NVD aún no ha analizado esta CVE; no son CPE verificados.

Linux — Linux Kernel^AI

Referencias

JSON original (NVD)

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  "id": "CVE-2026-72323",
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  "published": "2026-08-15T06:22:05.333",
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  "vulnStatus": "Received",
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nipv4: igmp: Fix potential UAF in igmp_gq_start_timer()\n\nA race condition exists between device teardown (inetdev_destroy) and\nincoming IGMP query processing (igmp_rcv), leading to a Use-After-Free\nin the IGMP timer callback.\n\nDuring device destruction, inetdev_destroy() drops the primary reference\nto in_device, which can drop its refcount to 0. The actual freeing of\nin_device memory is deferred via RCU (using call_rcu()).\n\nConcurrently, igmp_rcv() runs under RCU read lock and obtains the\nin_device pointer. Because the memory is RCU-protected, CPU-0 can safely\ndereference in_device even if its refcount has hit 0.\n\nHowever, if CPU-0 calls igmp_gq_start_timer() and re-arms the timer, it\nattempts to acquire a reference using in_dev_hold(). This increments the\nrefcount from 0 to 1, triggering a \"refcount_t: addition on 0\" warning.\nSince the in_device memory is still scheduled to be freed after the RCU\ngrace period (as the free callback does not check the refcount again),\nthe device is freed while the timer is still armed. When the timer\nexpires, it accesses the freed memory, causing a kernel panic.\n\nFix this by using refcount_inc_not_zero() (via a new helper\nin_dev_hold_safe()) to prevent acquiring a reference if the device is\nalready being destroyed. If the refcount is 0, we do not arm the timer.\n\nA similar issue in IPv6 MLD is fixed in a subsequent patch."
    }
  ],
  "lastModified": "2026-09-02T13:18:07.997",
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}