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CVE-2026-89929
KVM: nVM: Ensure INVVPID is emulated on the correct physical CPU
Published 2026-09-16 (33 days ago) by the Linux kernel CNA. Subsystem arch/x86. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-89929 in every release this site tracks, and what each one means in practice. Every status below is the one the Debian Security Team publishes for this CVE. source
| Release | Status | Version | What this means |
|---|---|---|---|
| Debian 12bookworm | vulnerable | 6.1.190-1 | No fix published anywhere yet, neither in Debian nor upstream for the series bookworm tracks. Watch the Debian tracker page for this CVE. Advisories for bookworm have historically landed a median of 23 days after publication. |
| Debian 13trixie | fixedDSA-6528-1 · 2026-09-29 · text | 6.12.111-1 | Update the kernel and reboot. DSA-6528-1 shipped the fix on 2026-09-29, in 6.12.111-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.2.6-1 | Update the kernel and reboot. Fixed in 7.2.6-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.2.6-1 | Update the kernel and reboot. Fixed in 7.2.6-1. A running kernel keeps the old code until the machine restarts. |
| Debian 12bookworm · linux-6.12 | fixedDLA-4817-1 · 2026-10-04 · text | 6.12.111-1~deb12u1 | Update the kernel and reboot. DLA-4817-1 shipped the fix on 2026-10-04, in 6.12.111-1~deb12u1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
When emulating INVVPID, KVM executes INVVPID on the physical CPU using vpid02 (instead of the L1 assigned VPID), after doing some validations on the operands. However, it is possible that the physical CPU KVM executes INVVPID on is different from the CPU L2 is running on. For example, in the following scenario: - L2 runs on CPU #1 and exits to L1 (vmx->nested.vmcs02.cpu=1) - L1 migrates to CPU #2 and executes INVVPID - KVM executes INVVPID on CPU #2 - L1 migrates back to CPU #1 and runs L2 (vmx->nested.vmcs02.cpu=1) The TLB entries on CPU #1 are never invalidated, because INVVPID was executed on CPU #2, and vmcs02 never ran on a different pCPU (i.e. vmx_vcpu_load_vmcs() will *not* request KVM_REQ_TLB_FLUSH). Ensure that INVVPID is being executed on the same pCPU that L2 last ran on, and if not, fallback to clearing last_vpid=0 to trigger a full VPID flush on the next nested VM-Enter (as KVM will detect L1 using a different VPID for L2). If L2 ends up running on a different pCPU, KVM will flush the TLB anyway through vmx_vcpu_load_vmcs().
Where it lives
The fix touches these files. If the subsystem is one you do not use, the practical exposure is lower, though the package is still the vulnerable one.
arch/x86/kvm/vmx/nested.c
- What this is
- KERNEL VIRTUAL MACHINE FOR X86 (KVM/x86)MAINTAINERS section matched on arch/x86/kvm/*/ · kvm@vger.kernel.org · Supported
Show whether Debian builds this, per release
Not established. This site could not find the build rule for the affected file in the kernel trees Debian ships, so it has no answer about whether Debian compiles this code. Read that as unknown, never as absent.
- bookworm, trixie, forky, sid, bookworm · linux-6.12?
- ?
- not established - no Makefile entry for the affected file
Where a release above reads "not established", no build rule for the affected file was found in that release's kernel tree. That is a gap in this lookup, not a finding that the code is absent.
From the configuration Debian publishes for every kernel flavour it builds. It covers only the architectures Debian ships a linux-config package for, and nothing about a kernel you built yourself. Debian's own status above stays authoritative about the source package.MAINTAINERS
Signals
- Published
- 2026-09-16 (33 days ago)source
- CVSS
- 8.8 high
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:Hsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.17%, higher than 5.7% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- arch/x86
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 4.4 | 6.12.110 | d03e721801ac |
| 4.4 | 6.18.51 | 27bdeb5fd190 |
| 4.4 | 7.2.5 | 9941850e8adf |
| 4.4 | 7.3 | 6d00e67326d8 |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4817-1 | 2026-10-04 | bookworm 6.12.111-1~deb12u1 | tracker |
| DSA-6528-1 | 2026-09-29 | trixie 6.12.111-1 | tracker |
Why the CNA scored it this way
Quoted from the kernel CNA's own scoring file, word for word. A highlighted metric carries the most severe value CVSS v3.1 defines for it, which is what pushes the score up. source
- AV:LAttack vector, local
- The bug is reached when an L1 nested VMX guest executes INVVPID, causing a VM-exit handled by handle_invvpid() on the host KVM_RUN ioctl path after VMXON/VMLAUNCH; no network, adjacent-radio, or physical path reaches this nVMX emulator.
- AC:LAttack complexity, low
- A kvm-group or nested-virt tenant attacker controls both sides: pin the vCPU, run L2, migrate the vCPU thread with sched_setaffinity, execute INVVPID in L1, then migrate back so L2 resumes on the original pCPU with stale VPID translations; nested=1 and vpid=1 are defaults.
- PR:LPrivileges required, low
- Exploitation needs /dev/kvm (kvm-group) or a cloud tenant VM with nested virtualization, plus CPL=0 in L1 after VMXON to execute INVVPID; KVM create/run ioctls have no CAP_SYS_ADMIN gate, and init-namespace host root is not required.
- UI:NUser interaction, none
- The attacker issues INVVPID from their own nested hypervisor and migrates the vCPU themselves; no separate victim action such as mounting a filesystem or opening a crafted file is required.
- S:CScope, changed
- Missed INVVPID leaves L2's VPID-tagged combined GVA-to-HPA TLB entries live on the pCPU where L2 last ran, so L2 can access host physical pages after L1 revoked those mappings, crossing the nested-guest versus L1-hypervisor and potentially guest-to-host isolation boundary.
- C:HConfidentiality impact, high
- Stale combined mappings let L2 read host physical memory that L1 unmapped or reassigned to L1 or a sibling L2, and with page reuse those frames may hold other-guest or host data, yielding cross-VM information disclosure rather than a bounded leak.
- I:HIntegrity impact, high
- The retained TLB entries remain writable, so L2 can write through stale translations into remapped or recycled pages including L1 hypervisor memory, giving an arbitrary-write primitive consistent with missed-TLB and nested isolation-bypass scoring.
- A:HAvailability impact, high
- Writes through stale VPID mappings into reused L1, sibling-guest, or host pages corrupt hypervisor or kernel state and can oops or panic the nested hypervisor or host, fully denying availability to co-resident VMs.