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CVE-2026-80553
s390/vfio_ccw: Cancel existing workqueues
Published 2026-08-26 (2 months ago) by the Linux kernel CNA. Subsystem drivers/s390. Debian urgency: not yet assigned.
Debian does not build this code. The per-release build detail is under "Where it lives" below.
What to do, per Debian release
Debian's own status for CVE-2026-80553 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-4777-1 · 2026-09-08 · text | 6.1.187-1 | Update the kernel and reboot. DLA-4777-1 shipped the fix on 2026-09-08, in 6.1.187-1. A running kernel keeps the old code until the machine restarts. |
| Debian 13trixie | fixed | 6.12.105-1 | Update the kernel and reboot. Fixed in 6.12.105-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.1.10-1 | Update the kernel and reboot. Fixed in 7.1.10-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.10-1 | Update the kernel and reboot. Fixed in 7.1.10-1. A running kernel keeps the old code until the machine restarts. |
| Debian 12bookworm · linux-6.12 | fixedDLA-4788-1 · 2026-09-19 · text | 6.12.107-1~deb12u1 | Update the kernel and reboot. DLA-4788-1 shipped the fix on 2026-09-19, in 6.12.107-1~deb12u1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
The initialization of the io_work and crw_work workqueues begs the question of whether they should be un-initialized. Add the corresponding cleanup tags in _release_dev to ensure work isn't dispatched after the private struct is free'd.
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.
drivers/s390/cio/vfio_ccw_ops.c
- What this is
- S390 VFIO-CCW DRIVERMAINTAINERS section matched on drivers/s390/cio/vfio_ccw* · linux-s390@vger.kernel.org · Supported
Check it on the machine
grep -wE 'CONFIG_S390|CONFIG_VFIO_CCW' /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.
Show whether Debian builds this, per release
Debian does not build this code. In 5 releases below, every kernel flavour Debian publishes has the switch off, so the vulnerable file is compiled into no kernel binary Debian ships.
- bookworm, trixie, forky, sid, bookworm · linux-6.12n
- n
- not enabled on any flavour - this release does not build the code
- Build switches
- CONFIG_S390, CONFIG_VFIO_CCW
- Reads as
- all on means the file is compiled; any one off means it is not.
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
- 2026-08-26 (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
- 0.18%, higher than 6.7% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- drivers/s390
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 4.12 | 5.10.267 | 87d569cb35a5 |
| 4.12 | 5.15.218 | 7492ca2d0c5d |
| 4.12 | 6.1.185 | b94b28c1f0fa |
| 4.12 | 6.6.153 | e868ea8be0bc |
| 4.12 | 6.12.105 | dc47a98abe67 |
| 4.12 | 6.18.46 | b7ae0f799386 |
| 4.12 | 7.1.10 | 77f5e888d2e6 |
| 4.12 | 7.2 | 79c60b2c6110 |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4788-1 | 2026-09-19 | bookworm 6.12.107-1~deb12u1 | tracker |
| DLA-4777-1 | 2026-09-08 | bookworm 6.1.187-1 | 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 bug is reached only through local VFIO mediated-device syscalls (read/write/ioctl on /dev/vfio/* and device fds) that start channel I/O or receive CRW events; vfio-ccw has no network, Bluetooth, or physical-bus packet entry point.
- AC:LAttack complexity, low
- This is a close/teardown versus workqueue race where the VFIO client controls both sides: it can submit I/O that queues io_work/crw_work via interrupts or path events, then close or release the device while work is still pending, and retry to win reliably.
- PR:LPrivileges required, low
- Exploitation requires access to an opened vfio-ccw mdev (typical QEMU/libvirt VM operator or delegated /dev/vfio holder on an IBM Z passthrough host), not init-namespace root; mdev creation is admin setup, but triggering the UAF needs only the delegated VFIO fd.
- UI:NUser interaction, none
- No separate victim action is required; once vfio-ccw passthrough is configured, the attacker issues channel I/O and coordinates device close/release (e.g., hot-unplug or fd teardown) without needing another user to mount media or click anything.
- S:CScope, changed
- On IBM Z/LinuxONE, vfio-ccw exists to pass DASD subchannels into KVM guests; guest-driven channel I/O causes host interrupt/workqueue activity and host-side teardown UAF corrupts hypervisor kernel memory outside the VM security boundary.
- C:HConfidentiality impact, high
- vfio_ccw_sch_io_todo() and vfio_ccw_crw_todo() dereference freed vfio_ccw_private fields (io_mutex, cp, io_region, crw list, eventfd pointers); per kernel UAF guidance this enables attacker-influenced reuse and arbitrary kernel read primitives.
- I:HIntegrity impact, high
- The UAF handlers perform mutex operations, cp_free(), memcpy into io_region, and eventfd_signal() on freed memory, giving heap-sprayable arbitrary write and control-flow hijack potential beyond a simple crash.
- A:HAvailability impact, high
- Use-after-free in deferred I/O/CRW work during device close or release can immediately oops or panic the host kernel from invalid mutex/structure access, and successful exploitation can hang or crash the system even when not leveraged for code execution.