CVE-2026-98118

netfs: Fix readahead synchronisation issues by loading all folios upfront

Published Sep 25, 2026 CVSS 3.1 · 7.1 High EPSS < 1% KEV · Not listed

Description

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

netfs: Fix readahead synchronisation issues by loading all folios upfront

There are some synchronisation issues that derive from the app thread
adding more folios to the rolling buffer whilst the collector thread is
looking at them or trying to clear them, such as determining the setting of
front_folio_order when the next folio hasn't been added yet,

The reason for the rolling buffer approach is that loading the buffer
upfront and then dropping all the refs just acquired is quite a slow
operation, and loading progressively allows some of the cost to be deferred
until after at least some of the I/O is started.

Instead, a better way is to load all the folios into the rolling buffer
upfront - and then drop the refs later, once the I/O is in progress. (Even
better would be for the refs not to be there at all.)

Fix this by changing the rolling buffer loader to load all the folios
selected by the VM for readahead upfront into the folio queue. The folio
queue is allocated a batch worth at a time as we don't know how many folios
are involved (the readahead_control struct, alas, has a page count, not a
folio count).

The folio refs acquired from readahead are then dropped in bulk once the
first subrequest is dispatched as it's quite a slow operation. The
collector waits for NETFS_RREQ_NEED_PUT_RA_REFS to be cleared so that it
doesn't unlock folios before the xarray has been scanned for them.

This simplifies the buffer handling later and isn't noticeably slower as
the xarray doesn't need to be modified and the folios are all already
pre-locked.

Analysis

Technical impact

The CVE describes a synchronization race in the netfs readahead subsystem of the Linux kernel. When the application thread adds folios to the rolling buffer while the collector thread is simultaneously examining or clearing that buffer, inconsistent ref counting can occur. Based on the description, it may lead to incomplete or missing folio processing, potentially causing unpredictable I/O behavior or kernel instability.

Affected Systems

All Linux kernel releases that implement the rolling buffer in netfs before the commit that introduced the fix are affected. This includes any distribution that ships one of those kernel versions.

Risk and Exploitability

The CVSS score of 7.1 indicates a high impact in terms of system stability, while the EPSS score of <1% suggests a very low chance of exploitation in the wild. The vulnerability is classified as CWE‑362 (Race Condition) and CWE‑366 (Concurrent Access to Unprotected Data). It is an internal race that does not provide a direct remote exploitation path and is not listed in CISA's KEV catalog.

Affected Products

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
`ee4cdf7ba857a894ad1650d6ab77669cbbfa329e`	affected	< 8c9b33945712074a85d3bdacbca036ba6b3d92c6
`ee4cdf7ba857a894ad1650d6ab77669cbbfa329e`	affected	< fed0b33e6c584986ba70018ec9f9787a98216e64

Linux

affected

Version	Status	Constraints
`6.12`	affected	—
`0`	unaffected	< 6.12
`7.2.7`	unaffected	≤ 7.2.*
`7.3`	unaffected	≤ *

Configuration 1 [-]

OR	cpe:2.3:o:linux:linux_kernel::::::::
	cpe:2.3:o:linux:linux_kernel:7.3:rc1::::::
	cpe:2.3:o:linux:linux_kernel:7.3:rc2::::::

No data.

Vendor Product Versions

Linux

Linux Kernel

Version	Status	Scheme	Platform
`[ee4cdf7ba857a894ad1650d6ab77669cbbfa329e,8c9b33945712074a85d3bdacbca036ba6b3d92c6)`	affected	code_commit	—
`[ee4cdf7ba857a894ad1650d6ab77669cbbfa329e,fed0b33e6c584986ba70018ec9f9787a98216e64)`	affected	code_commit	—

Linux

Linux Kernel

Version	Status	Scheme	Platform
`6.12`	affected	generic	—
`[0,6.12)`	unaffected	generic	—
`[7.2.7,7.3.0]`	unaffected	semver	—
`[7.3-rc3,*]`	unaffected	semver	—

Remediation

No solution or workaround provided in the CVE record.

OpenCVE Recommended Actions

Apply a kernel patch that includes commit 8c9b33945712074a85d3bdacbca036ba6b3d92c6 or upgrade to a later kernel release that contains the netfs readahead fix.
If a kernel upgrade cannot be performed immediately, reduce or disable netfs readahead usage by adjusting mount options or disabling the subsystem to limit concurrent access patterns that trigger the race.
Continuously monitor kernel logs (e.g., dmesg, /var/log/kern.log) for netfs or folio handling anomalies and apply the patch as soon as it becomes available.

Generated by OpenCVE AI on October 28, 2026 at 18:11 UTC.

Tracking

Advisories

Source	ID	Title
Ubuntu USN	USN-9019-1	Linux kernel (Azure) vulnerabilities
Ubuntu USN	USN-9020-1	Linux kernel vulnerabilities

Metrics

No CVSS v4.0

Attack Vector Local

Attack Complexity Low

Privileges Required Low

Scope Unchanged

Confidentiality Impact High

Integrity Impact None

Availability Impact High

User Interaction None

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

Exploit prediction score: < 1% (0.091% probability within 30 days)

Key SSVC decision points have not yet been added.

References

Link	Providers
https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-98118.mbox
https://git.kernel.org/stable/c/8c9b33945712074a85d3bdacbca036ba6b3d92c6
https://git.kernel.org/stable/c/fed0b33e6c584986ba70018ec9f9787a98216e64
https://nvd.nist.gov/vuln/detail/CVE-2026-98118
https://www.cve.org/CVERecord?id=CVE-2026-98118

History

Oct 28, 2026 4:15 PM Weaknesses updated. Affected versions updated. Scoring metrics updated View changes

Type	Values Removed	Values Added
Weaknesses		CWE-362
CPEs		cpe:2.3:o:linux:linux_kernel:7.3:rc1:::::: cpe:2.3:o:linux:linux_kernel:7.3:rc2::::::
Metrics	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'}`	cvssV3_1 `{'score': 7.1, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H'}`

Sep 29, 2026 9:15 PM Weaknesses updated View changes

Type	Values Removed	Values Added
Weaknesses	CWE-368

Sep 29, 2026 1:15 PM Weaknesses updated. Added references. Scoring metrics updated View changes

Type	Values Removed	Values Added
Weaknesses		CWE-366
References		https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-98118.mbox https://nvd.nist.gov/vuln/detail/CVE-2026-98118 https://www.cve.org/CVERecord?id=CVE-2026-98118
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 `Moderate`

Sep 25, 2026 1:15 PM Weaknesses updated View changes

Type	Values Removed	Values Added
Weaknesses		CWE-368

Sep 25, 2026 10:45 AM Description updated. Title updated. First appearance in the feed. Affected versions updated. Affected vendors updated. Added references View changes

Type	Values Removed	Values Added
Description		In the Linux kernel, the following vulnerability has been resolved: netfs: Fix readahead synchronisation issues by loading all folios upfront There are some synchronisation issues that derive from the app thread adding more folios to the rolling buffer whilst the collector thread is looking at them or trying to clear them, such as determining the setting of front_folio_order when the next folio hasn't been added yet, The reason for the rolling buffer approach is that loading the buffer upfront and then dropping all the refs just acquired is quite a slow operation, and loading progressively allows some of the cost to be deferred until after at least some of the I/O is started. Instead, a better way is to load all the folios into the rolling buffer upfront - and then drop the refs later, once the I/O is in progress. (Even better would be for the refs not to be there at all.) Fix this by changing the rolling buffer loader to load all the folios selected by the VM for readahead upfront into the folio queue. The folio queue is allocated a batch worth at a time as we don't know how many folios are involved (the readahead_control struct, alas, has a page count, not a folio count). The folio refs acquired from readahead are then dropped in bulk once the first subrequest is dispatched as it's quite a slow operation. The collector waits for NETFS_RREQ_NEED_PUT_RA_REFS to be cleared so that it doesn't unlock folios before the xarray has been scanned for them. This simplifies the buffer handling later and isn't noticeably slower as the xarray doesn't need to be modified and the folios are all already pre-locked.
Title		netfs: Fix readahead synchronisation issues by loading all folios upfront
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/8c9b33945712074a85d3bdacbca036ba6b3d92c6 https://git.kernel.org/stable/c/fed0b33e6c584986ba70018ec9f9787a98216e64