CVE-2024-40953

Host crash via torn KVM vCPU index

Published Jul 12, 2024 · Updated Aug 5, 2026

Race condition in Linux KVM 2.6.39 and later allows guest OS users to crash the host through concurrent vCPU spin loops. The kvm_vcpu_on_spin function accesses last_boosted_vcpu without atomic operations, so a torn store can produce an out-of-bounds vCPU-array index. The flaw requires concurrent guest vCPU execution; dereferencing the resulting invalid pointer can panic the host and interrupt every VM on it.

CVSS severity7.9
High
EPSS probability0.20%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Race condition in Linux KVM 2.6.39 and later allows guest OS users to crash the host through concurrent vCPU spin loops. The kvm_vcpu_on_spin function accesses last_boosted_vcpu without atomic operations, so a torn store can produce an out-of-bounds vCPU-array index. The flaw requires concurrent guest vCPU execution; dereferencing the resulting invalid pointer can panic the host and interrupt every VM on it.

The record

CVE
CVE-2024-40953
Published
Jul 12, 2024
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-362, T1499.004
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Jul 12, 2024CVE publishedPublication date reported by the CVE source.
  2. Aug 5, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=217ece6129f2d3b4fdd18d9e79be9e43d8d14a42 <11a772d5376aa6d3e2e69b5b5c585f79b60c0e17
  2. Affected versionversion=217ece6129f2d3b4fdd18d9e79be9e43d8d14a42 <49f683b41f28918df3e51ddc0d928cb2e934ccdb
  3. Affected versionversion=217ece6129f2d3b4fdd18d9e79be9e43d8d14a42 <4c141136a28421b78f34969b25a4fa32e06e2180
  4. Affected versionversion=217ece6129f2d3b4fdd18d9e79be9e43d8d14a42 <71fbc3af3dacb26c3aa2f30bb3ab05c44d082c84
  5. Affected versionversion=217ece6129f2d3b4fdd18d9e79be9e43d8d14a42 <82bd728a06e55f5b5f93d10ce67f4fe7e689853a
  6. Affected versionversion=217ece6129f2d3b4fdd18d9e79be9e43d8d14a42 <92c77807d938145c7c3350c944ef9f39d7f6017c
  7. Affected versionversion=217ece6129f2d3b4fdd18d9e79be9e43d8d14a42 <95c8dd79f3a14df96b3820b35b8399bd91b2be60
  8. Affected versionversion=217ece6129f2d3b4fdd18d9e79be9e43d8d14a42 <a937ef951bba72f48d2402451419d725d70dba20
  9. Affected versionversion=2.6.39

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=217ece6129f2d3b4fdd18d9e79be9e43d8d14a42 <11a772d5376aa6d3e2e69b5b5c585f79b60c0e17; version=217ece6129f2d3b4fdd18d9e79be9e43d8d14a42 <49f683b41f28918df3e51ddc0d928cb2e934ccdb; version=217ece6129f2d3b4fdd18d9e79be9e43d8d14a42 <4c141136a28421b78f34969b25a4fa32e06e2180; version=217ece6129f2d3b4fdd18d9e79be9e43d8d14a42 <71fbc3af3dacb26c3aa2f30bb3ab05c44d082c84; version=217ece6129f2d3b4fdd18d9e79be9e43d8d14a42 <82bd728a06e55f5b5f93d10ce67f4fe7e689853a; version=217ece6129f2d3b4fdd18d9e79be9e43d8d14a42 <92c77807d938145c7c3350c944ef9f39d7f6017c; version=217ece6129f2d3b4fdd18d9e79be9e43d8d14a42 <95c8dd79f3a14df96b3820b35b8399bd91b2be60; version=217ece6129f2d3b4fdd18d9e79be9e43d8d14a42 <a937ef951bba72f48d2402451419d725d70dba20; version=2.6.39

Published CVSS scores

7.9LinuxCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-362Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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