CVE-2026-89921

What the bug is

__kvm_inject_pfault_token() only sets .type and .u.ext.ext_params2 of the on-stack struct kvm_s390_irq but the full ext substructure is copied into the cpu local variable on inject. ext_params and pad contain stale stack values. Interrupt delivery only uses ext_params2, so nothing leaks to the guest, but a host user can use the migration ioctls to get to the data. Fix by zero-initializing the irq struct. Do the same for the inti data structure.

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/s390/kvm/kvm-s390.c

What this is

KERNEL VIRTUAL MACHINE for s390 (KVM/s390)MAINTAINERS section matched on arch/s390/kvm/ · kvm@vger.kernel.org · Supported

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 kvm

Prints 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.

• bookwormBnot built on arm64/rt/arm64, armhf/armmp, armhf/armmp-lpae, armhf/rt/armmp
• trixieBnot built on armel/rpi, armhf/armmp, armhf/armmp-lpae, armhf/rt/armmp
• forky, sidBnot built on armhf/armmp, armhf/armmp-lpae

B

built in on some, a module on others, absent on the rest

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

2026-09-16 (33 days ago)source

CVSS

no vector published, unrated

Attack vector

not published

EPSS

0.21%, higher than 10.3% of all CVEssource

CISA KEV

not listedthe KEV catalogue

Debian urgency

not yet assignedsource

Subsystem

arch/s390

Upstream fixes

The versions the CNA records as introducing and fixing this, and the commit for each. source

Introduced	Fixed in	Commit
3.19	6.12.112	b8abc760fa18
3.19	6.18.52	9b046de62b80
3.19	7.2.5	134f235e0e8d
3.19	7.3	4e2c7f7cbc27

Debian advisories