EUVD-2026-59674
GHSA-hf76-hfqm-mx9q
Severity by source
AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
AC:H reflects the multi-condition race (virtio_balloon + suspend timing + memory pressure); local vector and PR:L retained as suspend requires local access.
Primary rating from Vendor (Linux).
CVSS VectorVendor: Linux
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Lifecycle Timeline
5DescriptionCVE.org
In the Linux kernel, the following vulnerability has been resolved:
mm/page_reporting: use system_freezable_wq to fix UAF during suspend
During PM freeze (e.g. S3 suspend or S4 hibernation), device drivers like virtio_balloon reset their underlying virtio devices and delete their virtqueues via vdev->config->del_vqs().
However, page reporting work (page_reporting_process) was scheduled on the global system_wq. Because system_wq lacks the WQ_FREEZABLE flag, the PM freezer skips it, leaving page_reporting_process active during suspend.
If pages are freed into the buddy allocator while suspending (for example, when core MM invokes the balloon shrinker during S4 hibernation image saving), page reporting triggers virtballoon_free_page_report() on deleted virtqueues, resulting in a Use-After-Free / General Protection Fault:
[ 196.795226] general protection fault, probably for non-canonical address 0xaa1436fe70dae6df: 0000 [#1] SMP NOPTI [ 196.825967] Workqueue: events page_reporting_process [ 196.831038] RIP: 0010:virtqueue_add_split+0x233/0x4c0 [virtio_ring] [ 196.927073] virtballoon_free_page_report+0x3a/0xe0 [virtio_balloon] [ 196.946943] page_reporting_process+0x370/0x4f0
Fix this by switching page reporting work to system_freezable_wq. This ensures that the PM freezer pauses page_reporting_process before device drivers destroy their reporting virtqueues. Because the reporting worker is frozen, memory reclamation/freeing (e.g. via shrinker execution) can safely return pages to MM during freeze without triggering unfrozen reporting work on deleted virtqueues.
This aligns with the driver's existing design. The comment in virtballoon_freeze() states: /*
- The workqueue is already frozen by the PM core before this
- function is called.
*/
Testing: I have verified these fixes using Google’s virtualization infrastructure by running continuous suspend/resume iterations (40+ cycles) while churning memory using stress-ng (stress-ng --vm 4 --vm-bytes 60% --timeout 1) to constantly create free pages for the buddy allocator. We also set the page_reporting_order parameter to 0 to make the page reporting worker highly sensitive, forcing it to pick up any 4K free pages. This confirmed that the UAF crashes are no longer reproducible.
AnalysisAI
Use-After-Free in the Linux kernel's mm/page_reporting subsystem triggers a General Protection Fault during PM suspend and hibernation on systems running virtio_balloon with page reporting enabled. When the PM freezer initiates a suspend or S4 hibernation cycle, the virtio_balloon driver tears down its virtqueues via del_vqs(), but page_reporting_process - scheduled on the non-freezable system_wq workqueue - remains active. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires all of the following concurrent conditions: (1) The Linux guest kernel must have CONFIG_PAGE_REPORTING compiled in and the virtio_balloon driver loaded - this is common in KVM/QEMU guests but not present on bare-metal systems or non-virtio hypervisors. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The CVSS 3.1 score of 7.8 (AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H) reflects the theoretical maximum impact of a kernel UAF - memory corruption that could enable privilege escalation or kernel code execution. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | A virtualized Linux guest (e.g., a KVM/QEMU VM with virtio_balloon enabled) initiates a suspend-to-RAM (S3) or hibernation (S4) cycle - either via operator command or automated power management. During the freeze phase, the virtio_balloon driver deletes its virtqueues, but the page_reporting_process worker continues executing on system_wq. … |
| Remediation | The primary fix is to upgrade the Linux kernel to a patched stable release: 6.6.151, 6.12.103, 6.18.44, 7.1.8, or 7.2-rc6 or later, depending on the running stable series. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours, identify and inventory all Linux systems with virtio_balloon enabled-primarily virtualization hosts and guest systems-and document their current kernel versions. …
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