EUVD-2026-80557
GHSA-pgcj-5wj3-jcmr
Severity by source
AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
Triggered only by privileged host AP-config removal (PR:H, AV:L); scope changes to the KVM guest (S:C) which retains bounded unauthorized crypto access (C:L/I:L); no availability/DoS impact (A:N).
Primary rating from Vendor (Linux).
CVSS VectorVendor: Linux
Lifecycle Timeline
6DescriptionCVE.org
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.
AnalysisAI
Stale hardware access to unplugged crypto resources in Linux KVM guests on IBM Z (s390) stems from a logic error in the vfio-ap mediated-device driver: when the last AP adapter, domain, or control domain is removed from the host's AP configuration, the shadow APCB is cleared but the bitmap_andnot() return value is false for an empty result, so the do_hotplug flag never gets set and the guest's APCB is never refreshed. Only s390 hosts with CEX crypto adapters configured for guest passthrough are affected, exploitation is local and requires privileged host management access to modify the AP configuration, and no public exploit code has been identified at time of analysis. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Requires the s390 vfio-ap driver in use with a KVM guest assigned AP crypto resources via an mdev, AND a host-side operation that removes the LAST assigned AP adapter, domain, or control domain from the host's AP configuration - that specific 'resulting bitmap becomes empty' case is what triggers the skipped guest APCB update. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | This is a functional/isolation logic bug in the s390 vfio-ap crypto passthrough driver, not a memory-corruption or remote-code-execution flaw. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | Full exploit scenario with step-by-step reproduction available after sign-in. |
| Remediation | Apply the vendor-released kernel fixes: upgrade to Linux 6.1.188, 6.6.157, 6.12.110, 6.18.51, 7.2.5, or 7.3-rc1 (or later), or cherry-pick the relevant stable commit for your branch - f58e824de8577fe411f6199d659731a0f86a7275, 3a9b049bbdc40165d7f3e20b818eec95e5694d96, 753aa3bb1273bc0d36adb013d5915cc8ff6b72a9, c45753c32d452d10d8efaeb52587e9e6e8126e33, 04b35dd88c108b2d2ceaaa396aba1cb4049d5831, or 917f509bfb88048094dbb85c4e9dbc4d6fe4a886, per https://git.kernel.org/stable/. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours, identify all IBM Z (s390) hosts running Linux KVM with CEX crypto adapters configured for guest passthrough and apply the vendor-released patch for the Linux kernel vfio-ap driver (refer to the vendor advisory for the exact version) or isolate affected guests if patching cannot be done immediately. …
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