CVE-2026-64183 - Vulnerability Details

- efi: Allocate runtime workqueue before ACPI init

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.

Published: 2026-07-19

Score: 5.5 Medium

EPSS: < 1% Very Low

KEV: No

Impact:

Action:

Analysis

Impact

The Linux kernel contains a null pointer dereference that occurs when ACPI firmware calls are processed before the EFI runtime workqueue is allocated. This flaw can trigger a kernel panic during system startup, preventing the machine from booting normally. The weakness is a null pointer dereference (CWE‑476).

Affected Systems

All Linux kernel releases that allocate the EFI runtime workqueue after ACPI initialization are susceptible. This includes every publicly released kernel version prior to the patch that introduces the workqueue allocation during the postcore initcall, so any distribution running those kernel releases is potentially affected.

Risk and Exploitability

The CVSS score of 5.5 indicates medium severity, while the EPSS score of less than 1% signals a very low probability of exploitation in the field. The vulnerability is not listed in CISA’s KEV catalog. Because the fault occurs during subsystem initialization, an attacker would need local or physical influence of the firmware or boot environment, making it a boot‑time denial‑of‑service vector rather than a remote attack.

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

Vendor Product Default status Versions

Linux

unaffected

Version	Status	Constraints
`5894cf571e14fb393a4d0a82538de032127b9d8b`	affected	< 29cd94e678fcb3c4fd0f359deeac6d61334323fc
`5894cf571e14fb393a4d0a82538de032127b9d8b`	affected	< 6996e954ae830f5b793ba6cf449885ca519dbdd2
`5894cf571e14fb393a4d0a82538de032127b9d8b`	affected	< c32a1fbe0f9a48453a552bb315cc4f1e7a74084e
`5894cf571e14fb393a4d0a82538de032127b9d8b`	affected	< e871549f7894ad4114b3dd53f241aa25a268ba8b
`5894cf571e14fb393a4d0a82538de032127b9d8b`	affected	< 13c6da02e767152c9ac4330962247a5e47011035

Linux

affected

Version	Status	Constraints
`6.6`	affected	—
`0`	unaffected	< 6.6
`6.6.142`	unaffected	≤ 6.6.*
`6.12.92`	unaffected	≤ 6.12.*
`6.18.34`	unaffected	≤ 6.18.*
`7.0.11`	unaffected	≤ 7.0.*
`7.1`	unaffected	≤ *

No data.

Vendor Product Confidence Versions

Linux

Linux Kernel

99%

Version	Status	Scheme	Platform
`[5894cf571e14fb393a4d0a82538de032127b9d8b,29cd94e678fcb3c4fd0f359deeac6d61334323fc)`	affected	code_commit	—
`[5894cf571e14fb393a4d0a82538de032127b9d8b,6996e954ae830f5b793ba6cf449885ca519dbdd2)`	affected	code_commit	—
`[5894cf571e14fb393a4d0a82538de032127b9d8b,c32a1fbe0f9a48453a552bb315cc4f1e7a74084e)`	affected	code_commit	—
`[5894cf571e14fb393a4d0a82538de032127b9d8b,e871549f7894ad4114b3dd53f241aa25a268ba8b)`	affected	code_commit	—
`[5894cf571e14fb393a4d0a82538de032127b9d8b,13c6da02e767152c9ac4330962247a5e47011035)`	affected	code_commit	—

Linux

Linux Kernel

99%

Version	Status	Scheme	Platform
`6.6`	affected	generic	—
`[0,6.6)`	unaffected	generic	—
`[6.6.142,6.7.0)`	unaffected	semver	—
`[6.12.92,6.13.0)`	unaffected	semver	—
`[6.18.34,6.19.0)`	unaffected	semver	—
`[7.0.11,7.1.0)`	unaffected	semver	—
`[7.1,*]`	unaffected	generic	—

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Remediation

No vendor fix or workaround currently provided.

OpenCVE Recommended Actions

Update the kernel to a release that includes commit 5894cf571e14, such as kernel 6.8.x or later.
If using a custom kernel, backport the relevant commit into the local kernel tree and rebuild.
As a temporary workaround, disable ACPI by adding the kernel parameter 'acpi=off' to avoid early firmware calls that could trigger the null pointer dereference.

Generated by OpenCVE AI on July 30, 2026 at 20:00 UTC.

Tracking

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Advisories

Source	ID	Title
Ubuntu USN	USN-8593-1	Linux kernel vulnerabilities
Ubuntu USN	USN-8603-1	Linux kernel (Azure) vulnerabilities
Ubuntu USN	USN-8618-1	Linux kernel vulnerabilities

No CVSS v4.0

Attack Vector Local

Attack Complexity Low

Privileges Required Low

Scope Unchanged

Confidentiality Impact None

Integrity Impact None

Availability Impact High

User Interaction None

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

The EPSS score is 0.00164.

Key SSVC decision points have not yet been added.

References

Link	Providers
https://git.kernel.org/stable/c/13c6da02e767152c9ac4330962247a5e47011035
https://git.kernel.org/stable/c/29cd94e678fcb3c4fd0f359deeac6d61334323fc
https://git.kernel.org/stable/c/6996e954ae830f5b793ba6cf449885ca519dbdd2
https://git.kernel.org/stable/c/c32a1fbe0f9a48453a552bb315cc4f1e7a74084e
https://git.kernel.org/stable/c/e871549f7894ad4114b3dd53f241aa25a268ba8b
https://lore.kernel.org/linux-cve-announce/2026071939-CVE-2026-64183-ffa6@gregkh/T
https://nvd.nist.gov/vuln/detail/CVE-2026-64183
https://www.cve.org/CVERecord?id=CVE-2026-64183

History

Mon, 20 Jul 2026 12:15:00 +0000

Type	Values Removed	Values Added
Weaknesses		CWE-476
References		https://lore.kernel.org/linux-cve-announce/2026071939-CVE-2026-64183-ffa6@gregkh/T https://nvd.nist.gov/vuln/detail/CVE-2026-64183 https://www.cve.org/CVERecord?id=CVE-2026-64183
Metrics	threat_severity `None`	cvssV3_1 `{'score': 5.5, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H'}` threat_severity `Low`

Sun, 19 Jul 2026 16:15:00 +0000

Type	Values Removed	Values Added
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.
Title		efi: Allocate runtime workqueue before ACPI init
First Time appeared		Linux Linux linux Kernel
CPEs		cpe:2.3:o:linux:linux_kernel::::::::
Vendors & Products		Linux Linux linux Kernel
References		https://git.kernel.org/stable/c/13c6da02e767152c9ac4330962247a5e47011035 https://git.kernel.org/stable/c/29cd94e678fcb3c4fd0f359deeac6d61334323fc https://git.kernel.org/stable/c/6996e954ae830f5b793ba6cf449885ca519dbdd2 https://git.kernel.org/stable/c/c32a1fbe0f9a48453a552bb315cc4f1e7a74084e https://git.kernel.org/stable/c/e871549f7894ad4114b3dd53f241aa25a268ba8b

Subscriptions

Linux Linux Kernel

MITRE

Status: PUBLISHED

Assigner: Linux

Published: 2026-07-19T15:41:05.896Z

Updated: 2026-07-19T15:41:05.896Z

Reserved: 2026-07-19T07:54:57.039Z

Link: CVE-2026-64183

Vulnrichment

No data.

NVD

No data.

Redhat

Severity : Low

Publid Date: 2026-07-19T00:00:00Z

Links: CVE-2026-64183 - Bugzilla

OpenCVE Enrichment

Updated: 2026-07-30T20:15:05Z

Weaknesses

CWE-476
NULL Pointer Dereference

Impact

Affected Systems

Risk and Exploitability

Tracking

Attack Vector Local

Attack Complexity Low

Privileges Required Low

Scope Unchanged

Confidentiality Impact None

Integrity Impact None

Availability Impact High

User Interaction None

Subscriptions

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