CVE-2026-31787 (GCVE-0-2026-31787)
Vulnerability from cvelistv5
Published
2026-04-30 10:31
Modified
2026-05-04 07:46
Severity ?
VLAI Severity ?
EPSS score ?
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() 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
References
Impacted products
| Vendor | Product | Version | ||
|---|---|---|---|---|
| Linux | Linux |
Version: d71f513985c22f1050295d1a7e4327cf9fb060da Version: d71f513985c22f1050295d1a7e4327cf9fb060da Version: d71f513985c22f1050295d1a7e4327cf9fb060da Version: d71f513985c22f1050295d1a7e4327cf9fb060da Version: d71f513985c22f1050295d1a7e4327cf9fb060da Version: d71f513985c22f1050295d1a7e4327cf9fb060da Version: d71f513985c22f1050295d1a7e4327cf9fb060da Version: d71f513985c22f1050295d1a7e4327cf9fb060da |
||
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"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nxen/privcmd: fix double free via VMA splitting\n\nprivcmd_vm_ops defines .close (privcmd_close), but neither .may_split\nnor .open. When userspace does a partial munmap() on a privcmd mapping,\nthe kernel splits the VMA via __split_vma(). Since may_split is NULL,\nthe split is allowed. vm_area_dup() copies vm_private_data (a pages\narray allocated in alloc_empty_pages()) into the new VMA without any\nfixup, because there is no .open callback.\n\nBoth VMAs now point to the same pages array. When the unmapped portion\nis closed, privcmd_close() calls:\n - xen_unmap_domain_gfn_range()\n - xen_free_unpopulated_pages()\n - kvfree(pages)\n\nThe surviving VMA still holds the dangling pointer. When it is later\ndestroyed, the same sequence runs again, which leads to a double free.\n\nFix this issue by adding a .may_split callback denying the VMA split.\n\nThis is XSA-487 / CVE-2026-31787"
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Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
- Confirmed: The vulnerability is confirmed from an analyst perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
- Patched: This vulnerability was successfully patched by the user reporting the sighting.
- Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
- Not confirmed: The user expresses doubt about the veracity of the vulnerability.
- Not patched: This vulnerability was not successfully patched by the user reporting the sighting.
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