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CVE-2025-71080

Estado: ModificadaMedia (5.5)—

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

ipv6: fix a BUG in rt6_get_pcpu_route() under PREEMPT_RT

On PREEMPT_RT kernels, after rt6_get_pcpu_route() returns NULL, the current task can be preempted. Another task running on the same CPU may then execute rt6_make_pcpu_route() and successfully install a pcpu_rt entry. When the first task resumes execution, its cmpxchg() in rt6_make_pcpu_route() will fail because rt6i_pcpu is no longer NULL, triggering the BUG_ON(prev). It's easy to reproduce it by adding mdelay() after rt6_get_pcpu_route().

Using preempt_disable/enable is not appropriate here because ip6_rt_pcpu_alloc() may sleep.

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Fix this by handling the cmpxchg() failure gracefully on PREEMPT_RT: free our allocation and return the existing pcpu_rt installed by another task. The BUG_ON is replaced by WARN_ON_ONCE for non-PREEMPT_RT kernels where such races should not occur.

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).

Tecnologías afectadas (1)

Linux — Linux Kernel

CWE

Referencias

JSON original (NVD)

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  "id": "CVE-2025-71080",
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          "version": "3.1",
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          "baseSeverity": "HIGH",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
          "integrityImpact": "NONE",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
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          "value": "CWE-617"
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    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nipv6: fix a BUG in rt6_get_pcpu_route() under PREEMPT_RT\n\nOn PREEMPT_RT kernels, after rt6_get_pcpu_route() returns NULL, the\ncurrent task can be preempted. Another task running on the same CPU\nmay then execute rt6_make_pcpu_route() and successfully install a\npcpu_rt entry. When the first task resumes execution, its cmpxchg()\nin rt6_make_pcpu_route() will fail because rt6i_pcpu is no longer\nNULL, triggering the BUG_ON(prev). It's easy to reproduce it by adding\nmdelay() after rt6_get_pcpu_route().\n\nUsing preempt_disable/enable is not appropriate here because\nip6_rt_pcpu_alloc() may sleep.\n\nFix this by handling the cmpxchg() failure gracefully on PREEMPT_RT:\nfree our allocation and return the existing pcpu_rt installed by\nanother task. The BUG_ON is replaced by WARN_ON_ONCE for non-PREEMPT_RT\nkernels where such races should not occur."
    },
    {
      "lang": "es",
      "value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\nipv6: corregir un BUG en rt6_get_pcpu_route() bajo PREEMPT_RT\n\nEn kernels PREEMPT_RT, después de que rt6_get_pcpu_route() devuelve NULL, la tarea actual puede ser desalojada. Otra tarea ejecutándose en la misma CPU puede entonces ejecutar rt6_make_pcpu_route() e instalar exitosamente una entrada pcpu_rt. Cuando la primera tarea reanuda la ejecución, su cmpxchg() en rt6_make_pcpu_route() fallará porque rt6i_pcpu ya no es NULL, lo que activa el BUG_ON(prev). Es fácil reproducirlo añadiendo mdelay() después de rt6_get_pcpu_route().\n\nUsar preempt_disable/enable no es apropiado aquí porque ip6_rt_pcpu_alloc() puede dormir.\n\nSolucionar esto manejando el fallo de cmpxchg() de forma elegante en PREEMPT_RT: liberar nuestra asignación y devolver el pcpu_rt existente instalado por otra tarea. El BUG_ON es reemplazado por WARN_ON_ONCE para kernels que no son PREEMPT_RT donde tales condiciones de carrera no deberían ocurrir."
    }
  ],
  "lastModified": "2026-07-30T06:24:49.263",
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