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CVE-2026-52968
KVM: s390: pci: fix GAIT table indexing due to double-scaling pointer arithmetic
Published 2026-06-24 (4 months ago) by the Linux kernel CNA. Subsystem arch/s390. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-52968 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 | fixedDLA-4665-1 · 2026-07-03 · text | 6.1.176-1 | Update the kernel and reboot. DLA-4665-1 shipped the fix on 2026-07-03, 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 | 7.0.10-1 | Update the kernel and reboot. Fixed in 7.0.10-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.0.10-1 | Update the kernel and reboot. Fixed in 7.0.10-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
kvm_s390_pci_aif_enable(), kvm_s390_pci_aif_disable(), and aen_host_forward() index the GAIT by manually multiplying the index with sizeof(struct zpci_gaite). Since aift->gait is already a struct zpci_gaite pointer, this double-scales the offset, accessing element aisb*16 instead of aisb. This causes out-of-bounds accesses when aisb >= 32 (with ZPCI_NR_DEVICES=512) Fix by removing the erroneous sizeof multiplication.
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/interrupt.c
arch/s390/kvm/pci.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 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.
- 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
- 2026-06-24 (4 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
- 0.18%, higher than 6.6% 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 |
|---|---|---|
| 6.0 | 6.1.175 | 31a9d9f99428 |
| 6.0 | 6.6.141 | a99a25db131e |
| 6.0 | 6.12.91 | 11b8ff5b930b |
| 6.0 | 6.18.33 | b22a2da8792a |
| 6.0 | 7.0.10 | e7216651b94e |
| 6.0 | 7.1 | 16d990a15491 |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4671-1 | 2026-07-05 | bullseye 6.1.176-1~deb11u1 | tracker |
| DLA-4665-1 | 2026-07-03 | bookworm 6.1.176-1 | 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 vulnerable code is reached through local KVM/VFIO s390 zPCI management paths, specifically the `KVM_S390_ZPCI_OP` VM ioctl and host interrupt forwarding, not through network packets.
- AC:LAttack complexity, low
- Once zPCI AEN interpretation is available and an AISB index of 32 or higher is allocated, the bad pointer arithmetic deterministically accesses the wrong GAIT entry; no attacker-uncontrolled race is required.
- PR:LPrivileges required, low
- The attacker needs local ability to operate a KVM VM with an associated VFIO zPCI device or equivalent VM-management access, but the vulnerable ioctl itself does not require a real init-namespace root capability check.
- UI:NUser interaction, none
- After the attacker can issue the relevant KVM/VFIO operations or trigger adapter events for the assigned device, exploitation does not require a separate victim user action.
- S:CScope, changed
- This is KVM host-side memory corruption in a virtualization/device-assignment path, so a plausible exploit crosses the VM or assigned-device security boundary into host kernel resources.
- C:HConfidentiality impact, high
- The bug performs out-of-bounds reads from page-allocator memory through the misindexed GAIT entry and can expose host kernel memory contents or pointers.
- I:HIntegrity impact, high
- The registration and deregistration paths perform out-of-bounds writes to fields including `gisa`, `gisc`, `count`, `aisbo`, and `aisb`, making host kernel memory corruption and potential code execution defensible.
- A:HAvailability impact, high
- The same out-of-bounds reads and writes can corrupt arbitrary adjacent kernel memory or dereference corrupted physical addresses, making host crash or panic a high-probability impact.