CVE-2026-64017 - Vulnerability Details

- blk-mq: pop cached request if it is usable

Description

In the Linux kernel, the following vulnerability has been resolved:

blk-mq: pop cached request if it is usable

When submitting a bio to blk-mq, if the task should sleep after peeking
a cached request, but before it pops it, the plug flushes and calls
blk_mq_free_plug_rqs, freeing the cached_rqs. This creates a
use-after-free bug. Fix this by popping the cached request before any
possible blocking calls if it is suitable for use.

Popping this request first holds a queue reference, so avoid any
serialization races with queue freezes and can safely proceed with
dispatching that request to the driver. This potentially increases a
timing window from when a driver wants to freeze its queue to when
requests stop being dispatched. That scenario is off the fast path
though, and drivers need to appropriately handle requests during a
freeze request anyway.

The downside is the popped element needs to be individually freed when
we performed a bio plug merge. The cached request would have had to be
freed later anyway, but this patch does it inline with building the plug
list instead of after flushing it.

Published: 2026-07-19

Score: 7.8 High

EPSS: < 1% Very Low

KEV: No

Impact:

Action:

Analysis

Impact

The flaw impacts the Linux kernel’s blk‑mq subsystem. When a block I/O request is submitted, the kernel may free a cached request while the request is still active, creating a use‑after‑free condition that can corrupt kernel memory.

Affected Systems

Any Linux kernel that does not include the commits that patch the blk‑mq cached request handling code is vulnerable. Operating systems using any kernel version that lacks the fix, regardless of distribution, are at risk.

Risk and Exploitability

The CVSS score of 7.8 indicates high severity, and the EPSS score of less than 1% suggests a low likelihood of exploitation in the wild. The vulnerability is not listed in the CISA KEV catalog. The likely attack vector is a race condition occurring during block I/O operations that triggers the plug flush while a task sleeps, which can lead to a use‑after‑free.

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
`b0077e269f6c152e807fdac90b58caf012cdbaab`	affected	< 388468f7e7d1eab092cf2a39fdfb502e52019ec6
`b0077e269f6c152e807fdac90b58caf012cdbaab`	affected	< dc278e9bf2b9513a763353e6b9cc21e0f532954e
`b5c8e0ff76d10f6bf70a7237678f27c20cf59bc9`	affected	—
`e9c309ded295b7f8849097d71ae231456ca79f78`	affected	—
`b80056bd75a16e4550873ecefe12bc8fd190b1cf`	affected	—
`33cf52b6e53a6aa55883aa7fb9ceffceff8488a6`	affected	—
`8b6075046470c8756242dfe3fd058813636f69a3`	affected	—
`6.1.72`	affected	< 6.2
`6.5.13`	affected	< 6.6
`6.6.3`	affected	< 6.7
`6.1.75`	affected	< 6.2
`6.6.14`	affected	< 6.7

Linux

affected

Version	Status	Constraints
`6.7`	affected	—
`0`	unaffected	< 6.7
`7.0.11`	unaffected	≤ 7.0.*
`7.1`	unaffected	≤ *

No data.

Vendor Product Confidence Versions

Linux

Linux Kernel

99%

Version	Status	Scheme	Platform
`[b0077e269f6c152e807fdac90b58caf012cdbaab,388468f7e7d1eab092cf2a39fdfb502e52019ec6)`	affected	code_commit	—
`[b0077e269f6c152e807fdac90b58caf012cdbaab,dc278e9bf2b9513a763353e6b9cc21e0f532954e)`	affected	code_commit	—
`b5c8e0ff76d10f6bf70a7237678f27c20cf59bc9`	affected	code_commit	—
`e9c309ded295b7f8849097d71ae231456ca79f78`	affected	code_commit	—
`b80056bd75a16e4550873ecefe12bc8fd190b1cf`	affected	code_commit	—
`33cf52b6e53a6aa55883aa7fb9ceffceff8488a6`	affected	code_commit	—
`8b6075046470c8756242dfe3fd058813636f69a3`	affected	code_commit	—
`[6.1.72,6.2)`	affected	semver	—
`[6.5.13,6.6)`	affected	semver	—
`[6.6.3,6.7)`	affected	semver	—
`[6.1.75,6.2)`	affected	semver	—
`[6.6.14,6.7)`	affected	semver	—

Linux

Linux Kernel

99%

Version	Status	Scheme	Platform
`6.7`	affected	semver	—
`[0,6.7)`	unaffected	semver	—
`[7.0.11,7.1.0)`	unaffected	semver	—
`[7.1,*]`	unaffected	generic	—

Found an issue or want to improve our Enrichment? You can suggest it directly by opening an issue on our dedicated GitHub repository .

Remediation

No vendor fix or workaround currently provided.

OpenCVE Recommended Actions

Apply the latest Linux kernel update that contains the blk‑mq use‑after‑free fix.
Reboot the system after the update to load the corrected kernel.
If a new kernel version is not available, apply the patch that implements the commit 388468f7e7d1eab092cf2a39fdfb502e52019ec6 or backport it to your current kernel.

Generated by OpenCVE AI on August 4, 2026 at 06:12 UTC.

Tracking

Sign in to view the affected projects.

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 High

Integrity Impact High

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 0.0012.

Key SSVC decision points have not yet been added.

References

Link	Providers
https://git.kernel.org/stable/c/388468f7e7d1eab092cf2a39fdfb502e52019ec6
https://git.kernel.org/stable/c/dc278e9bf2b9513a763353e6b9cc21e0f532954e
https://lore.kernel.org/linux-cve-announce/2026071900-CVE-2026-64017-c8ee@gregkh/T
https://nvd.nist.gov/vuln/detail/CVE-2026-64017
https://www.cve.org/CVERecord?id=CVE-2026-64017

History

Sun, 26 Jul 2026 08:30:00 +0000

Type	Values Removed	Values Added
Weaknesses	CWE-416

Wed, 22 Jul 2026 00:15:00 +0000

Type	Values Removed	Values Added
Weaknesses		CWE-825
References		https://lore.kernel.org/linux-cve-announce/2026071900-CVE-2026-64017-c8ee@gregkh/T https://nvd.nist.gov/vuln/detail/CVE-2026-64017 https://www.cve.org/CVERecord?id=CVE-2026-64017
Metrics	threat_severity `None`	threat_severity `Important`

Tue, 21 Jul 2026 23:00:00 +0000

Type	Values Removed	Values Added
Weaknesses		CWE-416

Mon, 20 Jul 2026 14:45:00 +0000

Type	Values Removed	Values Added
Metrics		cvssV3_1 `{'score': 7.8, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H'}`

Sun, 19 Jul 2026 15:45:00 +0000

Type	Values Removed	Values Added
Description		In the Linux kernel, the following vulnerability has been resolved: blk-mq: pop cached request if it is usable When submitting a bio to blk-mq, if the task should sleep after peeking a cached request, but before it pops it, the plug flushes and calls blk_mq_free_plug_rqs, freeing the cached_rqs. This creates a use-after-free bug. Fix this by popping the cached request before any possible blocking calls if it is suitable for use. Popping this request first holds a queue reference, so avoid any serialization races with queue freezes and can safely proceed with dispatching that request to the driver. This potentially increases a timing window from when a driver wants to freeze its queue to when requests stop being dispatched. That scenario is off the fast path though, and drivers need to appropriately handle requests during a freeze request anyway. The downside is the popped element needs to be individually freed when we performed a bio plug merge. The cached request would have had to be freed later anyway, but this patch does it inline with building the plug list instead of after flushing it.
Title		blk-mq: pop cached request if it is usable
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/388468f7e7d1eab092cf2a39fdfb502e52019ec6 https://git.kernel.org/stable/c/dc278e9bf2b9513a763353e6b9cc21e0f532954e

Subscriptions

Linux Linux Kernel

MITRE

Status: PUBLISHED

Assigner: Linux

Published: 2026-07-19T15:39:11.989Z

Updated: 2026-08-05T12:38:14.493Z

Reserved: 2026-07-19T07:54:57.027Z

Link: CVE-2026-64017

Vulnrichment

No data.

NVD

No data.

Redhat

Severity : Important

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

Links: CVE-2026-64017 - Bugzilla

OpenCVE Enrichment

Updated: 2026-08-04T06:15:04Z

Weaknesses

CWE-825
Expired Pointer Dereference

Impact

Affected Systems

Risk and Exploitability

Tracking

Attack Vector Local

Attack Complexity Low

Privileges Required Low

Scope Unchanged

Confidentiality Impact High

Integrity Impact High

Availability Impact High

User Interaction None

Subscriptions

JSON object

JSON object

JSON object

JSON object

JSON object