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CVE-2026-89942
iio: buffer: Fix potential use-after-free in anonymous buffer release
Published 2026-09-16 (33 days ago) by the Linux kernel CNA. Subsystem drivers/iio. Debian urgency: unimportant.
What to do, per Debian release
Debian's own status for CVE-2026-89942 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 | fixedDSA-6528-1 · 2026-09-29 · text | 6.12.111-1 | Update the kernel and reboot. DSA-6528-1 shipped the fix on 2026-09-29, in 6.12.111-1. A running kernel keeps the old code until the machine restarts. |
| 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. |
| Debian 12bookworm · linux-6.12 | fixedDLA-4817-1 · 2026-10-04 · text | 6.12.111-1~deb12u1 | Update the kernel and reboot. DLA-4817-1 shipped the fix on 2026-10-04, in 6.12.111-1~deb12u1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
An anonymous buffer handle holds a reference to the underlying IIO device. The reference is dropped in the buffer handle's release function. If the device has been removed, either through unbind or hot-unplug, the buffer handle might hold the last reference. The release function takes the mutex for the buffer using a guard, which means the unlock happens after all the code in the function, including `iio_device_put()`. If the anonymous buffer holds the last reference this might free both the IIO device and the buffer, which contains the mutex, leading to use-after-free when the mutex is unlocked. Fix this by using a scoped guard just around the buffer dmabuf list access, making sure the mutex is unlocked before releasing the IIO device. Version 10 of the patch that introduced this issue used this exact scheme of first unlocking and then dropping the reference [1]. During review it was suggested to use a guard instead, and version 11 made that change [2].
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/iio/industrialio-buffer.c
- What this is
- IIO SUBSYSTEM AND DRIVERSMAINTAINERS section matched on drivers/iio/ · linux-iio@vger.kernel.org · Maintained
- Kernel module
- industrialio
Check it on the machine
grep -wE 'CONFIG_IIO|CONFIG_IIO_BUFFER' /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 industrialioPrints 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.
- bookwormMnot built on amd64/cloud-amd64, arm64/cloud-arm64
- trixie, forky, sidMnot built on amd64/cloud-amd64, arm64/cloud-arm64, s390x/s390x
- bookworm · linux-6.12Mnot built on amd64/cloud-amd64, arm64/cloud-arm64
- M
- a module where it is built at all; some flavours do not build it
- Build switches
- CONFIG_IIO, CONFIG_IIO_BUFFER
- 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
- 2026-09-16 (33 days ago)source
- CVSS
- 7.8 high
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/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
- drivers/iio
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 6.11 | 6.12.110 | ab53077511cd |
| 6.11 | 6.18.51 | f1f8f0e8e0af |
| 6.11 | 7.2.5 | 6d4bdbf7bad6 |
| 6.11 | 7.3 | 6288b593e76e |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4817-1 | 2026-10-04 | bookworm 6.12.111-1~deb12u1 | tracker |
| DSA-6528-1 | 2026-09-29 | trixie 6.12.111-1 | 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 attacker reaches the bug by opening /dev/iio:deviceX, issuing IIO_BUFFER_GET_FD_IOCTL to get an anonymous IIO buffer fd, then closing that fd after the IIO device is gone. That is a local char-device ioctl/close path, not a network or USB descriptor parser.
- AC:LAttack complexity, low
- This is a deterministic lifetime UAF, not a race: close() on the buffer fd unlocks buffer->dmabufs_mutex after iio_device_put() has already freed it. The attacker controls open/ioctl/close and can drop the last device reference by hot-unplugging a USB IIO or HID-sensor device they opened.
- PR:LPrivileges required, low
- iio_chrdev_open() and IIO_BUFFER_GET_FD_IOCTL perform no capability checks; access is only by /dev/iio:deviceX file mode. An unprivileged local user who can open that node (iio group, industrial DAQ, sensor HAL) can obtain the anonymous buffer fd.
- UI:NUser interaction, none
- The attacker opens the IIO device, obtains the buffer fd, removes the device, and closes the fd themselves. No separate victim action is required.
- S:UScope, unchanged
- The use-after-free is in kernel IIO buffer teardown and can escalate privileges only within the same kernel/OS authority. It does not cross a VM, IOMMU, or other security boundary.
- C:HConfidentiality impact, high
- Closing the anonymous buffer fd use-after-frees the IIO buffer object that embeds dmabufs_mutex. A kernel heap UAF can be reclaimed to build an arbitrary read primitive.
- I:HIntegrity impact, high
- The cleanup guard unlocks dmabufs_mutex after iio_dev_release() has already destroyed that mutex and freed the buffer, writing into freed kernel memory. That UAF is exploitable for heap corruption and control-flow hijack.
- A:HAvailability impact, high
- Use-after-free of the buffer mutex during anonymous-buffer release can oops or panic the kernel even without a fully controlled exploit, causing complete availability loss.