🛡️ CVE-2026-31787 — kernel

🟠 CVSS 7.8 — High ✅ No Known Exploit NVD
7.8
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

xen/privcmd: fix double free via VMA splitting

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

How this vulnerability can be exploited

This issue can be reached with local access to the system, attack complexity is low, an attacker needs low-level privileges on the target. No user interaction is required. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality high, integrity high, availability high.

Affected software

CVE-2026-31787 is recorded against 2 packages.

  • kernel (from 6.19.0 up to 7.0.3)
  • linux-kernel

Timeline and source

Published on 30 April 2026 and last revised on 15 July 2026. No public exploit is currently recorded for this entry. A vendor advisory or fix has been published. Record sourced from NVD.

References

www.openwall.com (Web)
git.kernel.org (Web)
git.kernel.org (Web)
git.kernel.org (Web)
git.kernel.org (Web)
git.kernel.org (Web)
git.kernel.org (Web)
git.kernel.org (Web)
git.kernel.org (Web)
xenbits.xen.org (Advisory)
github.com (Advisory)
nvd.nist.gov (Advisory)
git.kernel.org (Package)

CVE-2026-31787 on other distributions

Each distribution ships its own build and its own fixed version. Pick the one you run:

Details

Severity High
CVSS Score 7.8
CVSS Vector CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
CWE N/A
Public Exploit ✅ No
Source NVD
Published 2026-04-30
Updated 2026-08-12
Modified 2026-07-15

Affected Packages

Software From version Fixed in
kernel 6.19.0 7.0.3
linux-kernel — —

References

Similar Threats

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