CVE-2026-43133 (GCVE-0-2026-43133)
Vulnerability from cvelistv5
Published
2026-05-06 11:27
Modified
2026-08-26 12:04
Severity ?
7.9 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:H
Summary
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.
References
Impacted products
Vendor Product Version
Linux Linux Version: cc3ed80ae69f454c3d904af9f65394a540099723
Version: cc3ed80ae69f454c3d904af9f65394a540099723
Version: cc3ed80ae69f454c3d904af9f65394a540099723
Version: cc3ed80ae69f454c3d904af9f65394a540099723
Version: cc3ed80ae69f454c3d904af9f65394a540099723
Version: cc3ed80ae69f454c3d904af9f65394a540099723
Version: cc3ed80ae69f454c3d904af9f65394a540099723
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              "value": "AV:L - The vulnerable path is reached by locally running a KVM vCPU through /dev/kvm and executing nested SVM VMLOAD/VMSAVE from an L2 guest; it is not reachable via network packets.\nAC:L - The trigger is deterministic once nested SVM is available: configure L1 not to intercept VMLOAD/VMSAVE and execute the instruction in L2. No race or attacker-uncontrolled timing condition is required.\nPR:L - The attacker needs the ability to create/run a KVM VM or execute code in a nested guest, which is local low privilege where /dev/kvm is delegated. No real init-namespace root capability is required by the vulnerable emulation path itself.\nUI:N - After the VM/nested guest is running, exploitation is triggered solely by guest instruction execution. No additional victim user action is required.\nS:C - The bug is in KVM\u2019s enforcement of the nested virtualization boundary, where L2 execution causes KVM to operate on the wrong L0-maintained VMCB state. That can affect resources outside the L2 guest\u2019s own security authority.\nC:L - VMSAVE can copy bounded VMLOAD/VMSAVE save-state fields from the wrong internal VMCB into guest-accessible memory. I did not identify an arbitrary host-memory read primitive, so the defensible confidentiality impact is limited.\nI:L - VMLOAD can corrupt a bounded set of VMLOAD/VMSAVE state fields in the wrong KVM VMCB, causing incorrect nested guest/L1 state handling. I did not find a direct arbitrary host write or host code execution primitive.\nA:H - The wrong VMCB state can make nested VM execution fail or crash/hang the affected virtual machine/vCPU, and the attacker can trigger it repeatedly. This is a complete availability impact for the affected nested virtualization workload, even though I did not find a host kernel panic path."
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    "cveId": "CVE-2026-43133",
    "datePublished": "2026-05-06T11:27:20.882Z",
    "dateReserved": "2026-05-01T14:12:55.988Z",
    "dateUpdated": "2026-08-26T12:04:46.777Z",
    "state": "PUBLISHED"
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}


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