{
  "cveId": "CVE-2026-89960",
  "url": "https://patchblox.com/security/cve/CVE-2026-89960",
  "summary": "CVE-2026-89960 is fixed in 2 products on 1 platform, first by DEBIAN-CVE-2026-89960, released September 23, 2026. It is not reported as exploited. Patch Radar priority: High.",
  "title": "s390/vfio-ap: fix stale pqap_hook pointer on error in vfio_ap_mdev_set_kvm()",
  "description": "In the Linux kernel, the following vulnerability has been resolved:  s390/vfio-ap: fix stale pqap_hook pointer on error in vfio_ap_mdev_set_kvm()  In vfio_ap_mdev_set_kvm(), kvm-\u003Earch.crypto.pqap_hook is set to \u0026matrix_mdev-\u003Epqap_hook before the update locks are acquired and the mdev list is checked for a conflicting assignment. If another mdev is already attached to the same KVM instance, the function returns -EPERM without restoring the hook pointer, leaving kvm-\u003Earch.crypto.pqap_hook pointing at the failing matrix_mdev instead of the mdev that legitimately owns the KVM.  Since matrix_mdev-\u003Ekvm is never set on this error path, vfio_ap_mdev_unset_kvm() will not clean up the hook when matrix_mdev is later closed. If matrix_mdev is subsequently freed, any PQAP instruction executed by the guest will dereference the stale pointer through pqap_hook_rwsem, resulting in a use-after-free.  Since kvm-\u003Earch.crypto.pqap_hook is only set in the vfio_ap_mdev_set_kvm() function and is cleared in the vfio_ap_mdev_unset_kvm() function, a check for \u0027kvm-\u003Earch.crypto.pqap_hook != NULL\u0027 is all that is needed to determine whether it belongs to another mdev. This will alleviate the need to iterate the matrix_dev-\u003Emdev_list list to see if the kvm object is assigned to another mdev.This was introduced in v3 to alleviate the need to take the mdevs_lock while iterating the list; however, this did not prevent a potential race condition.  The pqap_hook_rwsem(write) is now performed inside get_update_locks_for_kvm(), which is updated to acquire pqap_hook_rwsem(write) between kvm-\u003Elock and mdevs_lock. This ordering is consistent with the PQAP intercept path, which acquires pqap_hook_rwsem in read mode while srcu is held under vcpu-\u003Emutex, establishing the dependency: kvm-\u003Elock -\u003E vcpu-\u003Emutex -\u003E srcu -\u003E pqap_hook_rwsem(read).  The pqap_hook_rwsem is now released inside the release_update_locks_for_kvm(), which is updated to release pqap_hook_rwsem(write) between mdevs_lock and kvm-\u003Elock.  Additionally, kvm_put_kvm() in vfio_ap_mdev_unset_kvm() is moved after release_update_locks_for_kvm(). Previously it was called while kvm-\u003Elock was held; if it were ever the last reference, kvm_destroy_vm() would run under kvm-\u003Elock, which would deadlock.",
  "published": "2026-09-16T11:17:06Z",
  "severity": "Important",
  "cvss": 8.8,
  "cvssVector": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H",
  "epss": 0.00171,
  "epssPercentile": 0.06513,
  "priority": "High",
  "priorityTier": 3,
  "exploited": false,
  "vendorExploited": false,
  "disclosed": false,
  "vendorAdvisory": "https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-89960",
  "fixes": [
    {
      "platform": "linux",
      "product": "linux",
      "release": "Debian 13.5 (trixie)",
      "fixedVersion": "6.12.111-1",
      "fix": "DEBIAN-CVE-2026-89960",
      "url": "https://patchblox.com/security/fix/linux/debian-cve-2026-89960",
      "released": "2026-09-23T19:19:02Z"
    },
    {
      "platform": "linux",
      "product": "linux",
      "release": "Debian 14",
      "fixedVersion": "7.2.6-1",
      "fix": "DEBIAN-CVE-2026-89960",
      "url": "https://patchblox.com/security/fix/linux/debian-cve-2026-89960",
      "released": "2026-09-23T19:19:02Z"
    },
    {
      "platform": "linux",
      "product": "linux-6.12",
      "release": "Debian 12.15 (bookworm)",
      "fixedVersion": "6.12.111-1~deb12u1",
      "fix": "DEBIAN-CVE-2026-89960",
      "url": "https://patchblox.com/security/fix/linux/debian-cve-2026-89960",
      "released": "2026-09-23T19:19:02Z"
    }
  ],
  "noFixYet": [],
  "dataAsOf": "2026-11-08T19:12:23Z",
  "attribution": {
    "text": "Data: Patchblox Patch Radar",
    "url": "https://patchblox.com/security/patch-radar",
    "terms": "https://patchblox.com/security/patch-radar/use-the-data"
  }
}