CVE-2026-89957

Description

In the Linux kernel, the following vulnerability has been resolved: s390/vfio-ap: Fix hot-unplug skipped when last AP adapter or domain removed The vfio_ap_mdev_hot_unplug_cfg() function uses the return value of bitmap_andnot() to determine whether the guest APCB needs to be updated. However, bitmap_andnot() returns false when the resulting destination bitmap is empty. This means that if the only adapter, domain or control domain assigned to an mdev is removed from the host's AP configuration, the bit is correctly cleared from the shadow APCB, but bitmap_andnot() returns false because the result is an empty bitmap. Consequently, do_hotplug remains 0 and vfio_ap_mdev_update_guest_apcb() is never called, leaving the KVM guest with stale hardware access to the unplugged AP devices. Fix this by replacing the bitmap_andnot() return value check with bitmap_intersects() to determine whether the shadow APCB actually overlaps with the removal mask. If there is an intersection, call bitmap_andnot() solely for its side effect of clearing the bits, then unconditionally set do_hotplug to trigger the guest APCB update.

Gravité et risque d'exploitation

CVE-2026-89957 obtient un score CVSS de 8.8/10, soit une gravité élevée. Selon le modèle EPSS, la probabilité qu'elle soit exploitée dans les 30 prochains jours est de 0.16 %, ce qui la place devant 5.3 % des CVE référencées.

Que faire ?

• Vérifiez si Linux (versions <=6.1.*, <=6.12.*, <3a9b049bbdc40165d7f3e20b818eec95e5694d96, 0, 6.1.188, 6.18.51, <=6.6.*, <917f509bfb88048094dbb85c4e9dbc4d6fe4a886, 6.0, 7.2.5, <04b35dd88c108b2d2ceaaa396aba1cb4049d5831, 6.6.157, <6.0, <=6.18.*, eeb386aeb5b7c8d2dae6a3ba49255d8a97803182, 6.12.110, <753aa3bb1273bc0d36adb013d5915cc8ff6b72a9, <=7.2.*, <f58e824de8577fe411f6199d659731a0f86a7275, <=*, <c45753c32d452d10d8efaeb52587e9e6e8126e33, 7.3) est présent sur votre parc.
• Appliquez le correctif ou la version corrigée indiqués dans les références de l'éditeur.
• À défaut de correctif, limitez l'exposition (filtrage réseau, désactivation du composant).
• Automatisez la détection : les agents CVE Heimdall (gratuits, open source) corrèlent l'inventaire de vos serveurs avec la base CVE.

Références

• https://git.kernel.org/stable/c/f58e824de8577fe411f6199d659731a0f86a7275
• https://git.kernel.org/stable/c/3a9b049bbdc40165d7f3e20b818eec95e5694d96
• https://git.kernel.org/stable/c/753aa3bb1273bc0d36adb013d5915cc8ff6b72a9
• https://git.kernel.org/stable/c/c45753c32d452d10d8efaeb52587e9e6e8126e33
• https://git.kernel.org/stable/c/04b35dd88c108b2d2ceaaa396aba1cb4049d5831
• https://git.kernel.org/stable/c/917f509bfb88048094dbb85c4e9dbc4d6fe4a886