Linux Kernel Xen Privcmd Double Free via VMA Splitting
CVE-2026-31787 Published on April 30, 2026
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
Products Associated with CVE-2026-31787
Want to know whenever a new CVE is published for Linux Kernel? stack.watch will email you.
Affected Versions
Linux:- Version 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and below dbf862ce9f009128ab86b234d91413a3e450beb4 is affected.
- Version 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and below 2b985d3a024b9e8c24e21671b34e855569763808 is affected.
- Version 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and below 1576ff3869cbd3620717195f971c85b7d7fd62b5 is affected.
- Version 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and below 402d84ad9e89bd4cbfd07ca8598532b7021daf95 is affected.
- Version 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and below 2894a351fe2ea8684919d36df3188b9a35e3926f is affected.
- Version 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and below 446ee446d9ae66f36e95c3c90bbcc4e56b94cde0 is affected.
- Version 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and below 71bf829800758a6e3889096e4754ef47ba7fc850 is affected.
- Version 5.10.254, <= 5.10.* is unaffected.
- Version 5.15.204, <= 5.15.* is unaffected.
- Version 6.1.170, <= 6.1.* is unaffected.
- Version 6.6.137, <= 6.6.* is unaffected.
- Version 6.12.85, <= 6.12.* is unaffected.
- Version 6.18.26, <= 6.18.* is unaffected.
- Version 7.0.3, <= 7.0.* is unaffected.