CVE-2026-64183

What the bug is

Since commit 5894cf571e14 ("acpi/prmt: Use EFI runtime sandbox to invoke PRM handlers") ACPI PRM calls are delegated to a workqueue which runs in a kernel thread, making it easier to detect and mitigate faulting memory accesses performed by the firmware. Rafael reports that such PRM accesses may occur before efisubsys_init() executes, which is where the workqueue is allocated, leading to NULL pointer dereferences. Since acpi_init() [which triggers the early PRM accesses] executes as a subsys_initcall() as well, and has its own dependencies that may be sensitive to initcall ordering, deferring acpi_init() is not an option. So instead, split off the workqueue allocation into its own postcore initcall, as this is the only missing piece to allow EFI runtime calls to be made. This ensures that EFI runtime call (including PRM calls) are accessible to all code running at subsys_initcall() level.

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/firmware/efi/efi.c

What this is

EXTENSIBLE FIRMWARE INTERFACE (EFI)MAINTAINERS section matched on drivers/firmware/efi/ · linux-efi@vger.kernel.org · Maintained

Check it on the machine

grep -w CONFIG_EFI /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 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.

• bookwormYnot built on ppc64el/powerpc64le
• trixieYnot built on armel/rpi, ppc64el/powerpc64le, ppc64el/powerpc64le-64k, s390x/s390x
• forky, sidYnot built on ppc64el/powerpc64le, ppc64el/powerpc64le-64k, s390x/s390x

Y

built in where it is built at all; some flavours do not build it

Build switch

CONFIG_EFI

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

2026-07-19 (3 months ago)source

CVSS

no vector published, unrated

Attack vector

not published

EPSS

0.12%, higher than 1.6% of all CVEssource

CISA KEV

not listedthe KEV catalogue

Debian urgency

unimportantsource

Subsystem

drivers/firmware

Upstream fixes

The versions the CNA records as introducing and fixing this, and the commit for each. source

Introduced	Fixed in	Commit
6.6	6.6.142	29cd94e678fc
6.6	6.12.92	6996e954ae83
6.6	6.18.34	c32a1fbe0f9a
6.6	7.0.11	e871549f7894
6.6	7.1	13c6da02e767