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CVE Record

CVE-2025-38506: KVM: Allow CPU to reschedule while setting per-page memory attributes

In the Linux kernel, the following vulnerability has been resolved: KVM: Allow CPU to reschedule while setting per-page memory attributes When running an SEV-SNP guest with a sufficiently large amount of memory (1TB+), the host can experience CPU soft lockups when running an operation in kvm_vm_set_mem_attributes() to set memory attributes on the whole range of guest memory. watchdog: BUG: soft lockup - CPU#8 stuck for 26s! [qemu-kvm:6372] CPU: 8 UID: 0 PID: 6372 Comm: qemu-kvm Kdump: loaded Not tainted 6.15.0-rc7.20250520.el9uek.rc1.x86_64 #1 PREEMPT(voluntary) Hardware name: Oracle Corporation ORACLE SERVER E4-2c/Asm,MB Tray,2U,E4-2c, BIOS 78016600 11/13/2024 RIP: 0010:xas_create+0x78/0x1f0 Code: 00 00 00 41 80 fc 01 0f 84 82 00 00 00 ba 06 00 00 00 bd 06 00 00 00 49 8b 45 08 4d 8d 65 08 41 39 d6 73 20 83 ed 06 48 85 c0 <74> 67 48 89 c2 83 e2 03 48 83 fa 02 75 0c 48 3d 00 10 00 00 0f 87 RSP: 0018:ffffad890a34b940 EFLAGS: 00000286 RAX: ffff96f30b261daa RBX: ffffad890a34b9c8 RCX: 0000000000000000 RDX: 000000000000001e RSI: 0000000000000000 RDI: 0000000000000000 RBP: 0000000000000018 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: ffffad890a356868 R13: ffffad890a356860 R14: 0000000000000000 R15: ffffad890a356868 FS: 00007f5578a2a400(0000) GS:ffff97ed317e1000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f015c70fb18 CR3: 00000001109fd006 CR4: 0000000000f70ef0 PKRU: 55555554 Call Trace: <TASK> xas_store+0x58/0x630 __xa_store+0xa5/0x130 xa_store+0x2c/0x50 kvm_vm_set_mem_attributes+0x343/0x710 [kvm] kvm_vm_ioctl+0x796/0xab0 [kvm] __x64_sys_ioctl+0xa3/0xd0 do_syscall_64+0x8c/0x7a0 entry_SYSCALL_64_after_hwframe+0x76/0x7e RIP: 0033:0x7f5578d031bb Code: ff ff ff 85 c0 79 9b 49 c7 c4 ff ff ff ff 5b 5d 4c 89 e0 41 5c c3 66 0f 1f 84 00 00 00 00 00 f3 0f 1e fa b8 10 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 2d 4c 0f 00 f7 d8 64 89 01 48 RSP: 002b:00007ffe0a742b88 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 000000004020aed2 RCX: 00007f5578d031bb RDX: 00007ffe0a742c80 RSI: 000000004020aed2 RDI: 000000000000000b RBP: 0000010000000000 R08: 0000010000000000 R09: 0000017680000000 R10: 0000000000000080 R11: 0000000000000246 R12: 00005575e5f95120 R13: 00007ffe0a742c80 R14: 0000000000000008 R15: 00005575e5f961e0 While looping through the range of memory setting the attributes, call cond_resched() to give the scheduler a chance to run a higher priority task on the runqueue if necessary and avoid staying in kernel mode long enough to trigger the lockup.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

This Linux KVM issue can cause host CPU soft lockups when very large SEV-SNP virtual machines change memory attributes. The visible business impact is availability risk on affected virtualization hosts, not confirmed data theft. Evidence points to a narrow operational trigger involving 1TB+ guest memory.

Executive priority

Treat as a targeted virtualization availability issue. Prioritize cloud, hosting, and sensitive workload platforms using SEV-SNP at large memory sizes. It is not supported by the sources as a broadly exploitable emergency.

Technical view

kvm_vm_set_mem_attributes() can loop over a large guest memory range without yielding CPU time. On SEV-SNP guests with sufficiently large memory, this may keep execution in kernel mode long enough to trigger watchdog soft lockups. The fix adds scheduler rescheduling during per-page attribute updates.

Likely exposure

Exposure is mainly Linux KVM hosts running SEV-SNP guests with very large memory, especially around 1TB or more. General Linux systems not using KVM, SEV-SNP, or large guest memory ranges appear less relevant from the provided evidence.

Exploitation context

The source bundle does not show KEV listing, public exploitation, exploit code, or remote attack details. The described trigger is an operational KVM memory-attribute operation from qemu-kvm on a host running a large SEV-SNP guest.

Researcher notes

Affected version data in the source bundle is inconsistent and sparse. Validate against upstream stable commits and distribution advisories. Focus reproduction and telemetry on whole-range memory attribute updates, qemu-kvm ioctl paths, watchdog soft lockups, and large SEV-SNP guests.

Mitigation direction

  • Apply a Linux stable kernel fix or distribution backport containing the referenced KVM change.
  • Prioritize KVM hosts running SEV-SNP guests with 1TB or more memory.
  • Check vendor or distribution advisories for exact fixed package versions.
  • Plan host reboots or live-migration windows according to normal kernel patch procedures.

Validation and detection

  • Inventory Linux KVM hosts and their running kernel versions.
  • Identify SEV-SNP guests with very large memory allocations.
  • Review host logs for CPU soft lockup messages involving qemu-kvm or kvm_vm_set_mem_attributes.
  • Confirm the deployed kernel includes one referenced stable commit or a vendor backport.
Prepared
Confidence
medium
Sources
5

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors
3Timeline events
0ADP providers
4Source links

Vulnerability timeline

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  2. CVE publishedCVE Program

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  3. CVE updatedCVE Program

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Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinux5a475554db1e476a14216e742ea2bdb77362d5d5, 5a475554db1e476a14216e742ea2bdb77362d5d5, 5a475554db1e476a14216e742ea2bdb77362d5d5unaffected
LinuxLinux6.8, 0, 6.12.39, 6.15.7, 6.16affected
Weakness

CWE details

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