{
  "threat_severity" : "Important",
  "public_date" : "2026-04-30T00:00:00Z",
  "bugzilla" : {
    "description" : "kernel: xen/privcmd: fix double free via VMA splitting",
    "id" : "2464092",
    "url" : "https://bugzilla.redhat.com/show_bug.cgi?id=2464092"
  },
  "cvss3" : {
    "cvss3_base_score" : "7.0",
    "cvss3_scoring_vector" : "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H",
    "status" : "draft"
  },
  "cwe" : "CWE-763",
  "details" : [ "In the Linux kernel, the following vulnerability has been resolved:\nxen/privcmd: fix double free via VMA splitting\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.\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)\nThe surviving VMA still holds the dangling pointer. When it is later\ndestroyed, the same sequence runs again, which leads to a double free.\nFix this issue by adding a .may_split callback denying the VMA split.\nThis is XSA-487 / CVE-2026-31787", "A flaw was found in the Linux kernel's xen/privcmd module. A local user could exploit this by performing a partial unmapping of a `privcmd` memory region. This action causes a Virtual Memory Area (VMA) to split, leading to duplicated internal memory pointers. As a result, the same memory can be freed twice, a condition known as a double free, which can cause system instability or a denial of service." ],
  "package_state" : [ {
    "product_name" : "Red Hat Enterprise Linux 10",
    "fix_state" : "Affected",
    "package_name" : "kernel",
    "cpe" : "cpe:/o:redhat:enterprise_linux:10"
  }, {
    "product_name" : "Red Hat Enterprise Linux 6",
    "fix_state" : "Not affected",
    "package_name" : "kernel",
    "cpe" : "cpe:/o:redhat:enterprise_linux:6"
  }, {
    "product_name" : "Red Hat Enterprise Linux 7",
    "fix_state" : "Affected",
    "package_name" : "kernel",
    "cpe" : "cpe:/o:redhat:enterprise_linux:7"
  }, {
    "product_name" : "Red Hat Enterprise Linux 7",
    "fix_state" : "Affected",
    "package_name" : "kernel-rt",
    "cpe" : "cpe:/o:redhat:enterprise_linux:7"
  }, {
    "product_name" : "Red Hat Enterprise Linux 8",
    "fix_state" : "Affected",
    "package_name" : "kernel",
    "cpe" : "cpe:/o:redhat:enterprise_linux:8"
  }, {
    "product_name" : "Red Hat Enterprise Linux 8",
    "fix_state" : "Affected",
    "package_name" : "kernel-rt",
    "cpe" : "cpe:/o:redhat:enterprise_linux:8"
  }, {
    "product_name" : "Red Hat Enterprise Linux 9",
    "fix_state" : "Affected",
    "package_name" : "kernel",
    "cpe" : "cpe:/o:redhat:enterprise_linux:9"
  }, {
    "product_name" : "Red Hat Enterprise Linux 9",
    "fix_state" : "Affected",
    "package_name" : "kernel-rt",
    "cpe" : "cpe:/o:redhat:enterprise_linux:9"
  } ],
  "references" : [ "https://www.cve.org/CVERecord?id=CVE-2026-31787\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-31787\nhttps://lore.kernel.org/linux-cve-announce/2026043034-CVE-2026-31787-f6cc@gregkh/T" ],
  "name" : "CVE-2026-31787",
  "csaw" : false
}