CVE-2026-64183 efi: Allocate runtime workqueue before ACPI init
A null pointer dereference in the Linux kernel EFI subsystem can cause a denial of service during early boot when ACPI PRM calls occur before workqueue allocation.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-64183?
CVE-2026-64183 is a medium-severity vulnerability in Linux kernel, published on 19 Jul 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
efi: Allocate runtime workqueue before ACPI init
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.
Weakness: CWE-476
Which versions are affected by CVE-2026-64183?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-64183?
Apply the vendor's patch.
Is CVE-2026-64183 being exploited?
There is no known exploitation of CVE-2026-64183 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2026-64183, DEBIAN-CVE-2026-64183, GHSA-wmr2-4wg6-fwrh, UBUNTU-CVE-2026-64183.