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CVE-2026-43116

Estado: ModificadaAlta (7.8)—

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

netfilter: ctnetlink: ensure safe access to master conntrack

Holding reference on the expectation is not sufficient, the master conntrack object can just go away, making exp->master invalid.

To access exp->master safely:

This patch goes for extending the nf_conntrack_expect_lock section to address this issue for simplicity, in the cases that are described below this is just slightly extending the lock section.

The add expectation command already holds a reference to the master conntrack from ctnetlink_create_expect().

However, the delete expectation command needs to grab the spinlock before looking up for the expectation. Expand the existing spinlock section to address this to cover the expectation lookup.

Leer descripción completaMostrar menos

Note that, the nf_ct_expect_iterate_net() calls already grabs the spinlock while iterating over the expectation table, which is correct.

The get expectation command needs to grab the spinlock to ensure master conntrack does not go away. This also expands the existing spinlock section to cover the expectation lookup too. I needed to move the netlink skb allocation out of the spinlock to keep it GFP_KERNEL.

For the expectation events, the IPEXP_DESTROY event is already delivered under the spinlock, just move the delivery of IPEXP_NEW under the spinlock too because the master conntrack event cache is reached through exp->master.

While at it, add lockdep notations to help identify what codepaths need to grab the spinlock.

Detalles técnicos trazas, registros y código del informe original
- Grab the nf_conntrack_expect_lock, this gets serialized with
  clean_from_lists() which also holds this lock when the master
  conntrack goes away.

- Hold reference on master conntrack via nf_conntrack_find_get().
  Not so easy since the master tuple to look up for the master conntrack
  is not available in the existing problematic paths.

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.

Vulnerabilidad local (AV:L, PR:L) de race condition (CWE-362) en netfilter que permite escalada de privilegios mediante acceso no sincronizado a estructuras de kernel; requiere privilegios locales pero no interacción del usuario.

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 ProgramExecution PreventionApplication Isolation and SandboxingExploit ProtectionUpdate Software

Tecnologías afectadas (1)

Linux — Linux Kernel

CWE

Referencias

JSON original (NVD)

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      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnetfilter: ctnetlink: ensure safe access to master conntrack\n\nHolding reference on the expectation is not sufficient, the master\nconntrack object can just go away, making exp->master invalid.\n\nTo access exp->master safely:\n\n- Grab the nf_conntrack_expect_lock, this gets serialized with\n  clean_from_lists() which also holds this lock when the master\n  conntrack goes away.\n\n- Hold reference on master conntrack via nf_conntrack_find_get().\n  Not so easy since the master tuple to look up for the master conntrack\n  is not available in the existing problematic paths.\n\nThis patch goes for extending the nf_conntrack_expect_lock section\nto address this issue for simplicity, in the cases that are described\nbelow this is just slightly extending the lock section.\n\nThe add expectation command already holds a reference to the master\nconntrack from ctnetlink_create_expect().\n\nHowever, the delete expectation command needs to grab the spinlock\nbefore looking up for the expectation. Expand the existing spinlock\nsection to address this to cover the expectation lookup. Note that,\nthe nf_ct_expect_iterate_net() calls already grabs the spinlock while\niterating over the expectation table, which is correct.\n\nThe get expectation command needs to grab the spinlock to ensure master\nconntrack does not go away. This also expands the existing spinlock\nsection to cover the expectation lookup too. I needed to move the\nnetlink skb allocation out of the spinlock to keep it GFP_KERNEL.\n\nFor the expectation events, the IPEXP_DESTROY event is already delivered\nunder the spinlock, just move the delivery of IPEXP_NEW under the\nspinlock too because the master conntrack event cache is reached through\nexp->master.\n\nWhile at it, add lockdep notations to help identify what codepaths need\nto grab the spinlock."
    }
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