Double Free Affecting linux-qemu-rc package, versions <7.1_rc3-r0


Severity

Recommended
0.0
high
0
10

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Threat Intelligence

EPSS
0.18% (9th percentile)

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  • Snyk IDSNYK-CHAINGUARDLATEST-LINUXQEMURC-16727881
  • published17 May 2026
  • disclosed30 Apr 2026

Introduced: 30 Apr 2026

CVE-2026-31787  (opens in a new tab)
CWE-415  (opens in a new tab)

How to fix?

Upgrade Chainguard linux-qemu-rc to version 7.1_rc3-r0 or higher.

NVD Description

Note: Versions mentioned in the description apply only to the upstream linux-qemu-rc package and not the linux-qemu-rc package as distributed by Chainguard. See How to fix? for Chainguard relevant fixed versions and status.

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

CVSS Base Scores

version 3.1