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CVE-2026-80572
Input: byd - synchronize timer deletion before freeing private data
Published 2026-08-26 (2 months ago) by the Linux kernel CNA. Subsystem drivers/input. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-80572 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 | fixedDSA-6477-1 · 2026-08-29 · text | 6.12.107-1 | Update the kernel and reboot. DSA-6477-1 shipped the fix on 2026-08-29, in 6.12.107-1. 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
byd_disconnect() uses timer_delete() before freeing the driver's private data. This does not wait for a running byd_clear_touch() callback, which dereferences the private data and its psmouse pointer. A callback racing with disconnect can therefore access the private data after it has been freed. The timer can also still be re-armed by byd_process_byte() while the disconnect is in progress. Use timer_shutdown_sync() before freeing the private data: it waits for a running callback and turns any later re-arm attempt into a no-op.
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/input/mouse/byd.c
- What this is
- INPUT (KEYBOARD, MOUSE, JOYSTICK, TOUCHSCREEN) DRIVERSMAINTAINERS section matched on drivers/input/ · linux-input@vger.kernel.org · Maintained
- Kernel module
- psmouse
Check it on the machine
grep -wE 'CONFIG_INPUT|CONFIG_INPUT_MOUSE|CONFIG_MOUSE_PS2|CONFIG_MOUSE_PS2_BYD' /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 psmousePrints 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.
- bookworm, trixie, forky, sid, bookworm · linux-6.12Bnot built on amd64/cloud-amd64, arm64/cloud-arm64
- B
- built in on some, a module on others, absent on the rest
- Build switches
- CONFIG_INPUT, CONFIG_INPUT_MOUSE, CONFIG_MOUSE_PS2, CONFIG_MOUSE_PS2_BYD
- 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
- 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
- 0.12%, higher than 1.7% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- drivers/input
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 4.6 | 6.1.185 | 84b205297fa1 |
| 4.6 | 6.6.154 | 28d984a66b9e |
| 4.6 | 6.12.106 | ee944a706a18 |
| 4.6 | 6.18.46 | 8dbfd8e32a13 |
| 4.6 | 7.1.10 | 2e509ef60ee4 |
| 4.6 | 7.2 | c83e79c0842e |
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 |
| DSA-6477-1 | 2026-08-29 | trixie 6.12.107-1 | 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
- Reachable from local PS/2 input: BYD packets enter via serio_interrupt() from built-in touchpad hardware or userio-emulated SERIO_8042 port; byd_process_byte()/byd_disconnect() are not network-exposed.
- AC:LAttack complexity, low
- An attacker can arm the 64ms byd_clear_touch timer via touch/relative packets while concurrently closing userio or unbinding the port to invoke byd_disconnect(), controlling both sides of the disconnect/timer race.
- PR:LPrivileges required, low
- Exploitation needs only local access to the PS/2 touchpad or /dev/userio to inject packets and trigger teardown; no init-namespace root, CAP_SYS_ADMIN, or write access to psmouse sysfs is required.
- UI:NUser interaction, none
- The attacker supplies touchpad traffic and drives device disconnect/emulation teardown themselves; no separate victim interaction (mount, plug-in approval, or click) is needed.
- S:UScope, unchanged
- Corruption stays within the host kernel address space during PS/2 driver teardown; it is standard local privilege escalation, not a guest-to-host or sandbox boundary crossing.
- C:HConfidentiality impact, high
- byd_clear_touch() dereferences freed byd_data (priv->psmouse) and can read attacker-reclaimed slab contents, enabling kernel pointer disclosure and broader arbitrary read primitives typical of heap use-after-free bugs.
- I:HIntegrity impact, high
- The timer callback writes into freed byd_data fields and may call input/report helpers through a stale psmouse pointer, giving heap corruption and a path to arbitrary kernel writes or control-flow hijacking.
- A:HAvailability impact, high
- Racing the timer with disconnect can cause invalid pointer dereferences, use-after-free access, kernel oops, or panic during input teardown; the condition is repeatable by re-arming the timer.