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Linux KernelOperating system · Linux

CVE-2026-31787

HIGH · 7.8 CVSS v3.1 Published 2026-04-30
Fix available
A fix is available. Upgrade to 5.10.254 / 5.15.204 or later.
See remediation →
80/100
Remediation priority · High
Zero-click Patch available

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis
How this class of weakness works · CWE-415

The same block of memory is freed twice, corrupting the allocator's bookkeeping in ways an attacker can shape toward code execution. It usually stems from tangled ownership of a pointer. The fix is clear, single ownership of each allocation and clearing pointers once they are freed.

General guidance for the double free class — the official description and references above are authoritative for this specific CVE. Want a bespoke review and a reviewed fix? Ask our team →

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Linux KernelOperating system
Affected:>= 3.8, < 5.10.254>= 5.11, < 5.15.204>= 5.16, < 6.1.170>= 6.2, < 6.6.137>= 6.7, < 6.12.85>= 6.13, < 6.18.26>= 6.19, < 7.0.3= 7.1

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Local
Complexity
Low
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 5.10.254 / 5.15.204 / 6.1.170 or later
Fixed in 5.10.2545.15.2046.1.170
Vendor patch git.kernel.org →
Recommended fix High confidence

Upgrade to kernel >= 5.10.254, 5.15.204, 6.1.170, or 6.6.137 depending on your current branch, or the latest stable release in your branch

  1. Identify the currently running kernel version using 'uname -r' or 'cat /proc/version'
  2. Check which stable branch your current kernel version belongs to (e.g., 5.10.x, 5.15.x, 6.1.x, 6.6.x)
  3. Upgrade the Linux kernel to a version >= 5.10.254 for 5.10.x releases, >= 5.15.204 for 5.15.x releases, >= 6.1.170 for 6.1.x releases, or >= 6.6.137 for 6.6.x releases
  4. Use your distribution's package manager to install the updated kernel (e.g., 'apt-get update && apt-get install linux-image-<version>' for Debian/Ubuntu, 'yum update kernel' for RHEL/CentOS, or 'zypper update kernel' for SUSE)
  5. Reboot the system to load the new kernel
  6. Verify the fix is applied by checking the kernel version and confirming the patch commit 1576ff3869cbd3620717195f971c85b7d7fd62b5 is included
Caveat Kernel upgrades may require system reboots and could have compatibility implications with custom modules or specific hardware drivers; ensure backup and test in non-production environment first

Generated from the published advisory — verify against the referenced sources before acting.

We can perform the upgrade in your staging environment and verify nothing breaks — typical engagement from $1,950. Get the upgrade done

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-31787 in production — separate from our analysis above.

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What this is

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  • Version or environment caveats, and links to real fixes
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