---
id: CVE-2026-31787
title: 'xen/privcmd: fix double free via VMA splitting'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  xen/privcmd: fix double free via VMA splitting

  privcmd_vm_ops defines .close (privcmd_close), but neither .may_split
  nor .open. When userspace does a partial munmap() …
severity: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= d71f513985c22f1050295d1a7e4327cf9fb060da <
    dbf862ce9f009128ab86b234d91413a3e450beb4
  - >-
    Linux >= d71f513985c22f1050295d1a7e4327cf9fb060da <
    2b985d3a024b9e8c24e21671b34e855569763808
  - >-
    Linux >= d71f513985c22f1050295d1a7e4327cf9fb060da <
    1576ff3869cbd3620717195f971c85b7d7fd62b5
  - >-
    Linux >= d71f513985c22f1050295d1a7e4327cf9fb060da <
    402d84ad9e89bd4cbfd07ca8598532b7021daf95
  - >-
    Linux >= d71f513985c22f1050295d1a7e4327cf9fb060da <
    2894a351fe2ea8684919d36df3188b9a35e3926f
  - >-
    Linux >= d71f513985c22f1050295d1a7e4327cf9fb060da <
    446ee446d9ae66f36e95c3c90bbcc4e56b94cde0
  - >-
    Linux >= d71f513985c22f1050295d1a7e4327cf9fb060da <
    71bf829800758a6e3889096e4754ef47ba7fc850
  - >-
    Linux >= d71f513985c22f1050295d1a7e4327cf9fb060da <
    24daca4fc07f3ff8cd0e3f629cd982187f48436a
  - Linux 3.8
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-11-06T15:25:39.751360Z'
exploitAvailable: true
published: '2026-04-30'
updated: '2026-11-06'
sourceUpdated: '2026-11-06T15:32:25.719Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-31787'
references:
  - url: 'https://git.kernel.org/stable/c/dbf862ce9f009128ab86b234d91413a3e450beb4'
  - url: 'https://git.kernel.org/stable/c/2b985d3a024b9e8c24e21671b34e855569763808'
  - url: 'https://git.kernel.org/stable/c/1576ff3869cbd3620717195f971c85b7d7fd62b5'
  - url: 'https://git.kernel.org/stable/c/402d84ad9e89bd4cbfd07ca8598532b7021daf95'
  - url: 'https://git.kernel.org/stable/c/2894a351fe2ea8684919d36df3188b9a35e3926f'
  - url: 'https://git.kernel.org/stable/c/446ee446d9ae66f36e95c3c90bbcc4e56b94cde0'
  - url: 'https://git.kernel.org/stable/c/71bf829800758a6e3889096e4754ef47ba7fc850'
  - url: 'https://git.kernel.org/stable/c/24daca4fc07f3ff8cd0e3f629cd982187f48436a'
tags:
  - cve.org
  - exploit-available
epss: 0.00183
epssPercentile: 0.07973
exploits:
  github: 1
  githubRepos:
    - 'https://github.com/0xAtharv/CVE-2026-31787'
  checkedAt: '2026-11-08T19:18:50.957Z'
ingestedAt: '2026-11-06T15:54:04.041Z'
---

## Overview

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

xen/privcmd: fix double free via VMA splitting

privcmd_vm_ops defines .close (privcmd_close), but neither .may_split
nor .open. When userspace does a partial munmap() on a privcmd mapping,
the kernel splits the VMA via __split_vma(). Since may_split is NULL,
the split is allowed. vm_area_dup() copies vm_private_data (a pages
array allocated in alloc_empty_pages()) into the new VMA without any
fixup, because there is no .open callback.

Both VMAs now point to the same pages array. When the unmapped portion
is closed, privcmd_close() calls:
    - xen_unmap_domain_gfn_range()
    - xen_free_unpopulated_pages()
    - kvfree(pages)

The surviving VMA still holds the dangling pointer. When it is later
destroyed, the same sequence runs again, which leads to a double free.

Fix this issue by adding a .may_split callback denying the VMA split.

This is XSA-487 / CVE-2026-31787

## Affected

- `Linux >= d71f513985c22f1050295d1a7e4327cf9fb060da < dbf862ce9f009128ab86b234d91413a3e450beb4`
- `Linux >= d71f513985c22f1050295d1a7e4327cf9fb060da < 2b985d3a024b9e8c24e21671b34e855569763808`
- `Linux >= d71f513985c22f1050295d1a7e4327cf9fb060da < 1576ff3869cbd3620717195f971c85b7d7fd62b5`
- `Linux >= d71f513985c22f1050295d1a7e4327cf9fb060da < 402d84ad9e89bd4cbfd07ca8598532b7021daf95`
- `Linux >= d71f513985c22f1050295d1a7e4327cf9fb060da < 2894a351fe2ea8684919d36df3188b9a35e3926f`
- `Linux >= d71f513985c22f1050295d1a7e4327cf9fb060da < 446ee446d9ae66f36e95c3c90bbcc4e56b94cde0`
- `Linux >= d71f513985c22f1050295d1a7e4327cf9fb060da < 71bf829800758a6e3889096e4754ef47ba7fc850`
- `Linux >= d71f513985c22f1050295d1a7e4327cf9fb060da < 24daca4fc07f3ff8cd0e3f629cd982187f48436a`
- `Linux 3.8`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.