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CVE-2026-89911
KVM: arm64: Correctly cap TLBI Range to the architural limit
Published 2026-09-16 (33 days ago) by the Linux kernel CNA. Subsystem arch/arm64. Debian urgency: unimportant.
What to do, per Debian release
Debian's own status for CVE-2026-89911 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 | not affected | 6.1.190-1 | Nothing to do. bookworm never shipped the vulnerable code. |
| Debian 13trixie | not affected | 6.12.113-1 | Nothing to do. trixie never shipped the vulnerable code. |
| 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. |
The vulnerability
What the bug is
TLB Invalidation by Range has a fairly powerful way of encoding pretty large ranges in a small number of bits. This range can be based on an arbitrary VA, which means it is pretty easy for a guest to generate an overflow should the hypervisor be naive enough to add the range to the base... Make sure the range is capped to the limit dictated by the address bit that determines the VA range. For an IPA invalidation, this is further corrected down the line to ignore the upper 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/include/asm/kvm_nested.h
- What this is
- KERNEL VIRTUAL MACHINE FOR ARM64 (KVM/arm64)MAINTAINERS section matched on arch/arm64/include/asm/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
- 2026-09-16 (33 days ago)source
- CVSS
- 7.9 high
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:Hsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.16%, higher than 4.6% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- unimportantsource
- 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 |
|---|---|---|
| 6.16 | 6.18.51 | 566b1f08d983 |
| 6.16 | 7.2.5 | 2de38f0448b4 |
| 6.16 | 7.3 | 69a598288195 |
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
- A nested arm64 guest reaches decode_range_tlbi() by executing a range TLBI (RVAE/RIPAS2 and related encodings) that traps through kvm_handle_sys_reg into handle_tlbi_el2/handle_ripas2e1is; this is local KVM vCPU execution via /dev/kvm, not a network, adjacent, or physical path.
- AC:LAttack complexity, low
- Once nested virt is available (kvm-arm.mode=nested and KVM_ARM_VCPU_HAS_EL2), the guest fully controls the TLBI operand and can deterministically encode a base+range that overflows the VA half-space; no race or attacker-uncontrollable timing is required.
- PR:LPrivileges required, low
- The attacker must run code in a nested-capable KVM guest or create such a VM through /dev/kvm (typically kvm-group). That is low privilege relative to the host; the emulated TLBI path does not require init-namespace root.
- UI:NUser interaction, none
- After the nested VM is running, exploitation is triggered solely by the guest executing the range TLBI; no additional host-user or victim action is required.
- S:CScope, changed
- The bug is in KVM’s nested-virtualization TLB/VNCR handling: an L1 TLBI is misapplied by L0, so host-maintained VNCR and related nested MMU state is not invalidated, crossing the guest/hypervisor security boundary.
- C:LConfidentiality impact, low
- A wrapping range causes missed VNCR invalidation, so L0 may keep using a stale guest page for EL2 sysreg state and expose that bounded nested-hypervisor data to a page L1 believed unmapped (for example reused by L2). This is not an arbitrary host-memory read.
- I:LIntegrity impact, low
- The host may keep writing nested EL2 sysreg state through the stale VNCR mapping into a guest page that should have been invalidated, corrupting bounded nested-virt state rather than providing an arbitrary host write or control-flow hijack.
- A:HAvailability impact, high
- Failed range invalidation leaves stale nested translations that can crash or hang the nested hypervisor or L2 workload, and the guest can repeat the TLBI at will, which is a complete availability loss for that nested VM.