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CVE-2026-72295
LoongArch: KVM: Validate irqchip index in irqfd routing
Published 2026-08-15 (2 months ago) by the Linux kernel CNA. Subsystem arch/loongarch. Debian urgency: unimportant.
What to do, per Debian release
Debian's own status for CVE-2026-72295 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 | 7.1.5-1 | Update the kernel and reboot. Fixed in 7.1.5-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.5-1 | Update the kernel and reboot. Fixed in 7.1.5-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
Sashiko reported that the irqchip index is not validated for LoongArch. Add validation and reject out-of-range irqchip indexes to avoid indexing past the routing table's chip array.
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/loongarch/kvm/irqfd.c
- What this is
- KERNEL VIRTUAL MACHINE FOR LOONGARCH (KVM/LoongArch)MAINTAINERS section matched on arch/loongarch/kvm/ · kvm@vger.kernel.org · Maintained
- Kernel module
- kvm
Check it on the machine
grep -w CONFIG_KVM /boot/config-$(uname -r)Reads the booted kernel's own configuration, on the machine and nowhere else. =y is built in, =m is a module, and an is not set line means the code is not there.
lsmod | grep -w kvmPrints a line if that module is loaded right now, and nothing if it is not. One that is not loaded can still be loaded later by anything that needs it.
Show whether Debian builds this, per release
Debian builds this, but not on every flavour. At least one release below builds the code on some of its kernel flavours and not on others, so the answer depends on the architecture and flavour installed. The build rule could not be established for 2 releases, so nothing is claimed about those.
- bookworm, trixie?
- forky, sidBnot built on armhf/armmp, armhf/armmp-lpae
- ?
- not established - no Makefile entry for the affected file
- B
- built in on some, a module on others, absent on the rest
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.
- Build switch
- CONFIG_KVM
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 kbuild Makefiles Debian linux-config packages
Signals
- Published
- 2026-08-15 (2 months 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 6.3% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- unimportantsource
- Subsystem
- arch/loongarch
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 6.13 | 6.18.40 | 199b570d7fca |
| 6.13 | 7.1.5 | 8b3e188d19e4 |
| 6.13 | 7.2 | 3474037904c2 |
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 out-of-bounds write is reached only via local KVM ioctls on /dev/kvm (KVM_CREATE_VM → KVM_SET_GSI_ROUTING with KVM_IRQ_ROUTING_IRQCHIP); no network, Bluetooth, or physical device path reaches kvm_set_routing_entry().
- AC:LAttack complexity, low
- One KVM_SET_GSI_ROUTING call with irqchip>=KVM_NR_IRQCHIPS (valid pin/gsi) deterministically executes rt->chip[irqchip][pin]=gsi past the chip[] boundary; the attacker fully controls irqchip, pin, and gsi with no race or uncontrollable layout.
- PR:LPrivileges required, low
- Exploitation requires only opening /dev/kvm and holding a VM fd (kvm group membership or CAP_SYS_ADMIN obtainable in a user namespace), matching unprivileged cloud tenants or QEMU service accounts—not init-namespace root.
- UI:NUser interaction, none
- No victim interaction is needed beyond the attacker's own KVM setup; a single malicious KVM_SET_GSI_ROUTING ioctl on a VM they control triggers the corruption.
- S:CScope, changed
- A KVM VM operator corrupts host kernel heap memory in the per-VM irq routing table from the KVM userspace interface, crossing the VM-to-host virtualization boundary rather than confining impact to the attacker's VM scope.
- C:HConfidentiality impact, high
- Unvalidated irqchip indexes cause out-of-bounds writes past chip[] into nr_rt_entries and map[] hlist metadata in a kmalloc'd routing table; per kernel guidance such heap corruption is leverageable for host kernel memory disclosure.
- I:HIntegrity impact, high
- The attacker controls both the OOB index (irqchip,pin) and written value (gsi), yielding targeted corruption of routing-table pointers/state that can be steered toward host privilege escalation or code execution.
- A:HAvailability impact, high
- Corrupting nr_rt_entries or map[] entries breaks subsequent irqfd/GSI routing lookups and irq injection, causing host kernel oops/panic or persistent VM/host denial of service on LoongArch KVM hosts.