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NVD / CVE Program· CNA Linux

CVE-2024-40953: KVM: Fix a data race on last_boosted_vcpu in kvm_vcpu_on_spin()

Noroxi assessment

Priority: Monitor (action score 18/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.19% (FIRST EPSS).
  • Someone with local access to the system can trigger it. A low-privileged account is enough. No user action is required. Special conditions such as timing or configuration are required.
  • Fixed version: Linux Linux 11a772d5376aa6d3e2e69b5b5c585f79b60c0e17, 49f683b41f28918df3e51ddc0d928cb2e934ccdb, 4c141136a28421b78f34969b25a4fa32e06e2180.
  • Severity is disputed: the assigning authority (CNA) scores it 7.9, NVD 4.7.
  • Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Low priority for now. Upgrade to Linux Linux 11a772d5376aa6d3e2e69b5b5c585f79b60c0e17, 49f683b41f28918df3e51ddc0d928cb2e934ccdb, 4c141136a28421b78f34969b25a4fa32e06e2180 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

In the Linux kernel, the following vulnerability has been resolved: KVM: Fix a data race on last_boosted_vcpu in kvm_vcpu_on_spin() Use {READ,WRITE}_ONCE() to access kvm->last_boosted_vcpu to ensure the loads and stores are atomic. In the extremely unlikely scenario the compiler tears the stores, it's theoretically possible for KVM to attempt to get a vCPU using an out-of-bounds index, e.g. if the write is split into multiple 8-bit stores, and is paired with a 32-bit load on a VM with 257 vCPUs: CPU0 CPU1 last_boosted_vcpu = 0xff; (last_boosted_vcpu = 0x100) last_boosted_vcpu[15:8] = 0x01; i = (last_boosted_vcpu = 0x1ff) last_boosted_vcpu[7:0] = 0x00; vcpu = kvm->vcpu_array[0x1ff]; As detected by KCSAN: BUG: KCSAN: data-race in kvm_vcpu_on_spin [kvm] / kvm_vcpu_on_spin [kvm] write to 0xffffc90025a92344 of 4 bytes by task 4340 on cpu 16: kvm_vcpu_on_spin (arch/x86/kvm/../../../virt/kvm/kvm_main.c:4112) kvm handle_pause (arch/x86/kvm/vmx/vmx.c:5929) kvm_intel vmx_handle_exit (arch/x86/kvm/vmx/vmx.c:? arch/x86/kvm/vmx/vmx.c:6606) kvm_intel vcpu_run (arch/x86/kvm/x86.c:11107 arch/x86/kvm/x86.c:11211) kvm kvm_arch_vcpu_ioctl_run (arch/x86/kvm/x86.c:?) kvm kvm_vcpu_ioctl (arch/x86/kvm/../../../virt/kvm/kvm_main.c:?) kvm __se_sys_ioctl (fs/ioctl.c:52 fs/ioctl.c:904 fs/ioctl.c:890) __x64_sys_ioctl (fs/ioctl.c:890) x64_sys_call (arch/x86/entry/syscall_64.c:33) do_syscall_64 (arch/x86/entry/common.c:?) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130) read to 0xffffc90025a92344 of 4 bytes by task 4342 on cpu 4: kvm_vcpu_on_spin (arch/x86/kvm/../../../virt/kvm/kvm_main.c:4069) kvm handle_pause (arch/x86/kvm/vmx/vmx.c:5929) kvm_intel vmx_handle_exit (arch/x86/kvm/vmx/vmx.c:? arch/x86/kvm/vmx/vmx.c:6606) kvm_intel vcpu_run (arch/x86/kvm/x86.c:11107 arch/x86/kvm/x86.c:11211) kvm kvm_arch_vcpu_ioctl_run (arch/x86/kvm/x86.c:?) kvm kvm_vcpu_ioctl (arch/x86/kvm/../../../virt/kvm/kvm_main.c:?) kvm __se_sys_ioctl (fs/ioctl.c:52 fs/ioctl.c:904 fs/ioctl.c:890) __x64_sys_ioctl (fs/ioctl.c:890) x64_sys_call (arch/x86/entry/syscall_64.c:33) do_syscall_64 (arch/x86/entry/common.c:?) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130) value changed: 0x00000012 -> 0x00000000

MediumCVSS 4.7 · v3.1—No exploit Fix available
Published
Jul 12, 2024
Updated
Aug 5, 2026
EPSS
0.1% · 9th percentile

Report tools

JSON

Action score

18

Monitor

Low priority for now.

CVSS
18 / 40 · 4.7 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.1%

CISA SSVC decision

Exploitation
none
Automatable
no
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
4.7
CNA · Linux
7.9
3.2 point gap

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:H

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

If any of these changes, we'll tell you in the daily email digest.

Follow CVE-2024-40953

When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
linuxlinux kernel

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • linux linux kernel2.6.39 and later · before 4.19.323
  • linux linux kernel4.20 and later · before 5.4.285
  • linux linux kernel5.5 and later · before 5.10.228
  • linux linux kernel5.11 and later · before 5.15.169
  • linux linux kernel5.16 and later · before 6.1.96
  • linux linux kernel6.2 and later · before 6.6.36
  • linux linux kernel6.7 and later · before 6.9.7
  • linux linux kernel6.10

Versions reported by the vendor

Affected version ranges reported by the assigning authority (Linux). Independent of NVD's CPE analysis and usually ahead of it.

  • Linux Linux

    • 2.6.39affected
    • 217ece6129f2d3b4fdd18d9e79be9e43d8d14a42 and later · before 11a772d5376aa6d3e2e69b5b5c585f79b60c0e17affected · git
    • 217ece6129f2d3b4fdd18d9e79be9e43d8d14a42 and later · before 4c141136a28421b78f34969b25a4fa32e06e2180affected · git
    • 217ece6129f2d3b4fdd18d9e79be9e43d8d14a42 and later · before 71fbc3af3dacb26c3aa2f30bb3ab05c44d082c84affected · git
    • 217ece6129f2d3b4fdd18d9e79be9e43d8d14a42 and later · before 82bd728a06e55f5b5f93d10ce67f4fe7e689853aaffected · git
    • 217ece6129f2d3b4fdd18d9e79be9e43d8d14a42 and later · before 92c77807d938145c7c3350c944ef9f39d7f6017caffected · git
    • 217ece6129f2d3b4fdd18d9e79be9e43d8d14a42 and later · before a937ef951bba72f48d2402451419d725d70dba20affected · git
    • 217ece6129f2d3b4fdd18d9e79be9e43d8d14a42 and later · before 95c8dd79f3a14df96b3820b35b8399bd91b2be60affected · git
    • 217ece6129f2d3b4fdd18d9e79be9e43d8d14a42 and later · before 49f683b41f28918df3e51ddc0d928cb2e934ccdbaffected · git
    • before 2.6.39not affected · semver

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Debian:11linuxbefore 5.10.234-15.10.234-1
Debian:12linuxbefore 6.1.99-16.1.99-1
Debian:13linuxbefore 6.9.7-16.9.7-1

Same product

linux: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-31431crypto: algif_aead - Revert to operating out-of-placeKEV
    90Now
  • CVE-2022-0847A flaw was found in the way the "flags" member of the new pipe buffer structure was lacking proper initialization in copy_page_to_iter_pipe KEV
    89Now
  • CVE-2021-22555Heap Out-Of-Bounds Write in Netfilter IP6T_SO_SET_REPLACEKEV
    85Now

Published before and after this one in the same product

  • ← EarlierCVE-2024-40951Jul 12, 2024 · ocfs2: fix NULL pointer dereference in ocfs2_abort_trigger()
    22Monitor
  • ← EarlierCVE-2024-40952Jul 12, 2024 · ocfs2: fix NULL pointer dereference in ocfs2_journal_dirty()
    22Monitor
  • Later →CVE-2024-40954Jul 12, 2024 · net: do not leave a dangling sk pointer, when socket creation fails
    31Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
Linux Linux11a772d5376aa6d3e2e69b5b5c585f79b60c0e17Vendor (CNA)
Linux Linux49f683b41f28918df3e51ddc0d928cb2e934ccdbVendor (CNA)
Linux Linux4c141136a28421b78f34969b25a4fa32e06e2180Vendor (CNA)
Linux Linux71fbc3af3dacb26c3aa2f30bb3ab05c44d082c84Vendor (CNA)
Linux Linux82bd728a06e55f5b5f93d10ce67f4fe7e689853aVendor (CNA)
Linux Linux92c77807d938145c7c3350c944ef9f39d7f6017cVendor (CNA)
Linux Linux95c8dd79f3a14df96b3820b35b8399bd91b2be60Vendor (CNA)
Linux Linuxa937ef951bba72f48d2402451419d725d70dba20Vendor (CNA)
debian:linux6.1.99-1 · Debian:12Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

No history yet (it accumulates with the daily EPSS job).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

National notice (Türkiye Cybersecurity Directorate / USOM)

Official security notices citing this record; remediation advice is on the agency's page.

All national notices →

Technical details

Attack conditions

  • Someone with local access to the system can trigger it.
  • A low-privileged account is enough.
  • No user action is required.
  • Special conditions such as timing or configuration are required.

If successful

Confidentiality
none
Integrity
none
Availability
high · the service can be disrupted
Attack vector
Local
Attack complexity
High
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality impact
None
Integrity impact
None
Availability impact
High

Weakness class (CWE)

CWE-362 · Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')

CVSS vector

CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H

nvd-primary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

ATT&CK techniques

—

Change log

  1. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (9 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records