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CVE-2026-64106
KVM: arm64: vgic-its: Reject restored DTE with out-of-range num_eventid_bits
Published 2026-07-19 (3 months ago) by the Linux kernel CNA. Subsystem arch/arm64. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-64106 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 | fixed | 6.1.176-1 | Update the kernel and reboot. Fixed in 6.1.176-1. A running kernel keeps the old code until the machine restarts. |
| Debian 13trixie | fixed | 6.12.94-1 | Update the kernel and reboot. Fixed in 6.12.94-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.0.12-1 | Update the kernel and reboot. Fixed in 7.0.12-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.0.12-1 | Update the kernel and reboot. Fixed in 7.0.12-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
Userspace can restore an ITS Device Table Entry whose Size field encodes more EventID bits than the virtual ITS supports. The live MAPD path rejects that state, but vgic_its_restore_dte() accepts it and stores the out-of-range value in dev->num_eventid_bits. Reject restored DTEs with num_eventid_bits > VITS_TYPER_IDBITS before allocating the device. This mirrors the MAPD check and prevents the restored state from reaching vgic_its_restore_itt(), where the unchecked value can be converted into an oversized scan_its_table() range.
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/arm64/kvm/vgic/vgic-its.c
- What this is
- KERNEL VIRTUAL MACHINE FOR ARM64 (KVM/arm64)MAINTAINERS section matched on arch/arm64/kvm/ · linux-arm-kernel@lists.infradead.org · Maintained
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?
- ?
- 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
- 2026-07-19 (3 months ago)source
- CVSS
- 9.0 critical
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:Hsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.15%, higher than 3.6% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- arch/arm64
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 4.12 | 6.1.175 | 1716b7fea2ea |
| 4.12 | 6.6.142 | dab9f93251b2 |
| 4.12 | 6.12.92 | b94538186a3e |
| 4.12 | 6.18.34 | 0680f5119265 |
| 4.12 | 7.0.11 | 8bcd15b690a3 |
| 4.12 | 7.1 | 9ce754ed8e7a |
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 only through the KVM device ioctl path (KVM_SET_DEVICE_ATTR with KVM_DEV_ARM_ITS_RESTORE_TABLES), which requires a local process with access to a VM file descriptor; it is not triggered by network packets or guest MMIO/ITS commands.
- AC:LAttack complexity, low
- An attacker can reliably plant a crafted Device Table Entry in guest RAM (Size field encoding 17–32 EventID bits) and have it processed during migration/snapshot restore; no race or attacker-uncontrollable memory layout is required, and the live MAPD path already proves the invalid state is straightforward to supply.
- PR:NPrivileges required, none
- The highest-impact scenario is a malicious cloud VM tenant who needs no host privileges: they write a malformed DTE directly into guest physical memory (bypassing MAPD validation) and trigger host-side restore during automated live migration or snapshot resume, without requiring /dev/kvm or root on the host.
- UI:NUser interaction, none
- Exploitation does not require victim interaction beyond normal hypervisor operations such as automated live migration or snapshot restore that the attacker can initiate as a VM tenant; no end-user action like opening a file is needed.
- S:CScope, changed
- The vulnerability crosses the VM security boundary because guest-controlled saved state causes the host kernel to perform an oversized ITS table scan and mass kernel allocations, impacting host availability outside the guest's security scope.
- C:HConfidentiality impact, high
- The unchecked num_eventid_bits value inflates scan_its_table()'s range up to BIT_ULL(32)*8 bytes (and can wrap the int size parameter for values 28–31), causing the host kernel to read far beyond the valid ITT bounds through kvm_read_guest_lock across a large guest GPA span.
- I:NIntegrity impact, none
- The flaw causes excessive guest-memory reads and kernel object allocation but does not corrupt or write host kernel memory; there is no demonstrated arbitrary host write, use-after-free, or code-execution primitive from this bug alone.
- A:HAvailability impact, high
- The oversized scan can loop for an enormous number of kvm_read_guest_lock iterations (worse when the truncated int size wraps to a huge unsigned length), and valid-looking restored ITEs can drive unbounded vgic_add_lpi/kzalloc allocations, exhausting host CPU and memory and causing severe denial of service.