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CVE-2025-21696

Estado: ModificadaMedia (5.5)—

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

mm: clear uffd-wp PTE/PMD state on mremap()

When mremap()ing a memory region previously registered with userfaultfd as write-protected but without UFFD_FEATURE_EVENT_REMAP, an inconsistency in flag clearing leads to a mismatch between the vma flags (which have uffd-wp cleared) and the pte/pmd flags (which do not have uffd-wp cleared). This mismatch causes a subsequent mprotect(PROT_WRITE) to trigger a warning in page_table_check_pte_flags() due to setting the pte to writable while uffd-wp is still set.

Fix this by always explicitly clearing the uffd-wp pte/pmd flags on any such mremap() so that the values are consistent with the existing clearing of VM_UFFD_WP.

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Be careful to clear the logical flag regardless of its physical form; a PTE bit, a swap PTE bit, or a PTE marker. Cover PTE, huge PMD and hugetlb 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).

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\nmm: clear uffd-wp PTE/PMD state on mremap()\n\nWhen mremap()ing a memory region previously registered with userfaultfd as\nwrite-protected but without UFFD_FEATURE_EVENT_REMAP, an inconsistency in\nflag clearing leads to a mismatch between the vma flags (which have\nuffd-wp cleared) and the pte/pmd flags (which do not have uffd-wp\ncleared).  This mismatch causes a subsequent mprotect(PROT_WRITE) to\ntrigger a warning in page_table_check_pte_flags() due to setting the pte\nto writable while uffd-wp is still set.\n\nFix this by always explicitly clearing the uffd-wp pte/pmd flags on any\nsuch mremap() so that the values are consistent with the existing clearing\nof VM_UFFD_WP.  Be careful to clear the logical flag regardless of its\nphysical form; a PTE bit, a swap PTE bit, or a PTE marker.  Cover PTE,\nhuge PMD and hugetlb paths."
    },
    {
      "lang": "es",
      "value": "En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: mm: borrar el estado PTE/PMD de uffd-wp en mremap() Al borrar con mremap() una región de memoria registrada previamente con userfaultfd como protegida contra escritura pero sin UFFD_FEATURE_EVENT_REMAP, una inconsistencia en la depuración de indicadores provoca una falta de coincidencia entre los indicadores vma (que tienen uffd-wp borrado) y los indicadores pte/pmd (que no tienen uffd-wp borrado). Esta falta de coincidencia hace que un mprotect(PROT_WRITE) posterior active una advertencia en page_table_check_pte_flags() debido a la configuración de pte como escribible mientras uffd-wp aún está configurado. Solucione esto borrando siempre explícitamente los indicadores pte/pmd de uffd-wp en cualquier mremap() de este tipo para que los valores sean coherentes con la depuración existente de VM_UFFD_WP. Tenga cuidado de borrar el indicador lógico independientemente de su forma física: un bit PTE, un bit PTE de intercambio o un marcador PTE. Cubra las rutas PTE, PMD enormes y TLB enormes."
    }
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  "lastModified": "2026-06-17T08:44:03.017",
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