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CVE-2026-74733
gpio: pca953x: fix pca953x_irq_bus_sync_unlock regmap lock
Published 2026-08-22 (2 months ago) by the Linux kernel CNA. Subsystem drivers/gpio. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-74733 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 | vulnerable | 6.1.190-1 | No fix published anywhere yet, neither in Debian nor upstream for the series bookworm tracks. Watch the Debian tracker page for this CVE. Advisories for bookworm have historically landed a median of 23 days after publication. |
| Debian 13trixie | vulnerable | 6.12.113-1 | No fix published anywhere yet, neither in Debian nor upstream for the series trixie tracks. Watch the Debian tracker page for this CVE. Advisories for trixie have historically landed a median of 11 days after publication. |
| Debian 14forky | fixed | 7.1.9-1 | Update the kernel and reboot. Fixed in 7.1.9-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.9-1 | Update the kernel and reboot. Fixed in 7.1.9-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
Locking is disabled in the regmap config as this driver uses its own lock. This means that all calls to regmap functions (read or write) must hold the i2c_lock. The function pca953x_irq_bus_sync_unlock() did not do this, and it was therefore possible that multiple threads could cause an incorrect register to be read/written. A previous patch partly fixed this, but only protected the write to the interrupt mask register, and not the read from the direction register.
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/gpio/gpio-pca953x.c
- What this is
- GPIO SUBSYSTEMMAINTAINERS section matched on drivers/gpio/ · linux-gpio@vger.kernel.org · Maintained
- Kernel module
- gpio_pca953x
Check it on the machine
grep -wE 'CONFIG_GPIOLIB|CONFIG_GPIO_PCA953X' /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 gpio_pca953xPrints 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 amd64/amd64, amd64/cloud-amd64, amd64/rt/amd64, arm64/cloud-arm64, i386/686, i386/686-pae, i386/rt/686-pae, ppc64el/powerpc64le
- trixieBnot built on amd64/amd64, amd64/cloud-amd64, amd64/rt/amd64, arm64/cloud-arm64, armel/rpi, ppc64el/powerpc64le, ppc64el/powerpc64le-64k, riscv64/riscv64, s390x/s390x
- forky, sidBnot built on amd64/amd64, amd64/cloud-amd64, amd64/rt-amd64, arm64/cloud-arm64, loong64/loong64, ppc64el/powerpc64le, ppc64el/powerpc64le-64k, s390x/s390x
- B
- built in on some, a module on others, absent on the rest
- Build switches
- CONFIG_GPIOLIB, CONFIG_GPIO_PCA953X
- 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
- 2026-08-22 (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
- 0.17%, higher than 6.3% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- drivers/gpio
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 6.10 | 6.18.57 | bf3f37c2d40b |
| 6.10 | 7.1.9 | e6a2f5f845f5 |
| 6.10 | 7.2 | 9dc325327bab |
| 6.1.101 | 0 | 0 |
| 6.6.42 | 0 | 0 |
| 6.9.11 | 0 | 0 |
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 pca953x_irq_bus_sync_unlock() path is reached only through local kernel interfaces—GPIO chardev ioctls (GPIO_V2_GET_LINE_IOCTL, GPIO_V2_LINE_SET_CONFIG_IOCTL, GPIO_V2_LINE_SET_VALUES_IOCTL), legacy sysfs GPIO, or concurrent in-kernel GPIO/IRQ ops—not via any network or physical bus-facing attack surface.
- AC:LAttack complexity, low
- An attacker drives both racing sides directly: one thread loops IRQ edge-detection setup/teardown (request_irq → irq_bus_sync_unlock) while another hammers GPIO value/direction writes holding i2c_lock; the original report reproduced the race ~1 in 1000 boots, so deliberate concurrency wins reliably.
- PR:LPrivileges required, low
- Exploitation requires an open file descriptor on /dev/gpiochipN or sysfs GPIO access; on embedded, industrial, medical, and automotive boards using pca953x expanders, udev routinely grants gpio group membership to unprivileged local users.
- UI:NUser interaction, none
- No victim interaction is required—the attacker performs all GPIO ioctl and IRQ configuration steps in its own threads without needing another user to mount, open, or configure devices.
- S:UScope, unchanged
- Corruption is confined to the kernel and the same on-board I2C GPIO expander; it does not cross VM, container, IOMMU, or other security-boundary scopes into a different authority.
- C:HConfidentiality impact, high
- With regmap disable_locking=true, the unprotected pca953x_read_regs() direction read races locked regmap paths, corrupting the maple regcache and returning data from the wrong register—yielding kernel heap UAF read and unintended register-state disclosure.
- I:HIntegrity impact, high
- Racing regmap transactions write interrupt-latch/direction data into wrong expander registers (documented output-register corruption), arbitrarily toggling safety-critical GPIO outputs; concurrent unsynchronized regcache writes provide a heap corruption/write primitive.
- A:HAvailability impact, high
- Concurrent regcache maple-tree corruption from unsynchronized regmap access can trigger kernel oops/panic via double-free; miswritten interrupt masks or direction registers can wedge expander IRQ handling and GPIO consumers in a persistent denial-of-service.