CVE-2026-72108 - Vulnerability Details

- dm thin metadata: fix metadata snapshot consistency on commit failure

Description

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

dm thin metadata: fix metadata snapshot consistency on commit failure

__reserve_metadata_snap() and __release_metadata_snap() modify the
superblock's held_root directly in the block_manager's buffer. If the
subsequent metadata commit fails, the held_root gets flushed to disk
through the abort_transaction path, resulting in inconsistent metadata.

Reproducer 1: __reserve_metadata_snap()

1. Create a 2 MiB metadata device and make the region after the 14th
block inaccessible, to trigger metadata commit failure in the
subsequent reserve_metadata_snap operation. The 14th block will be
the shadow destination for the index block.

dmsetup create tmeta --table "0 112 linear /dev/sdc 0
112 3984 error"

2. Create a 16 MiB thin-pool

dmsetup create tdata --table "0 32768 zero"
dd if=/dev/zero of=/dev/mapper/tmeta bs=4k count=1
dmsetup create tpool --table "0 32768 thin-pool /dev/mapper/tmeta \
/dev/mapper/tdata 128 0 1 skip_block_zeroing"

3. Take a metadata snapshot to trigger metadata commit failure and
transaction abort. However, the held_root is written to disk,
breaking metadata consistency.

dmsetup message tpool 0 "reserve_metadata_snap"

thin_check v1.2.2 result:

Bad reference count for metadata block 6. Expected 2, but space map contains 1.
Bad reference count for metadata block 7. Expected 2, but space map contains 1.
Bad reference count for metadata block 13. Expected 1, but space map contains 0.

Reproducer 2: __release_metadata_snap()

1. Create a 2 MiB metadata device and make the region after the 16th
block inaccessible, to trigger metadata commit failure in the
subsequent release_metadata_snap operation. The 16th block will be
the shadow destination for the index block.

dmsetup create tmeta --table "0 128 linear /dev/sdc 0
128 3968 error"

2. Create a 16 MiB thin-pool

dmsetup create tdata --table "0 32768 zero"
dd if=/dev/zero of=/dev/mapper/tmeta bs=4k count=1
dmsetup create tpool --table "0 32768 thin-pool /dev/mapper/tmeta \
/dev/mapper/tdata 128 0 1 skip_block_zeroing"

3. Reserve then release the metadata snapshot, to trigger metadata
commit failure and transaction abort. The held_root gets removed
from the on-disk superblock, causing inconsistent metadata.

dmsetup message tpool 0 "reserve_metadata_snap"
dmsetup message tpool 0 "release_metadata_snap"

thin_check v1.2.2 result:

Bad reference count for metadata block 6. Expected 1, but space map contains 2.
Bad reference count for metadata block 7. Expected 1, but space map contains 2.
1 metadata blocks have leaked.

Fix by deferring the held_root update to commit time.

Additionally, move the existing-snapshot check in __reserve_metadata_snap
before the shadow operation to avoid unnecessary work. In
__release_metadata_snap, clear pmd->held_root before btree deletion so
partial failure leaks blocks rather than leaving a stale reference, and
unlock the snapshot block before decrementing its refcount.

Published: 2026-08-15

Score: n/a

EPSS: < 1% Very Low

KEV: No

Impact:

Action:

Analysis

Analysis and contextual insights are available on OpenCVE Cloud.

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
`991d9fa02da0dd1f843dc011376965e0c8c6c9b5`	affected	< 4af993468193cf4cd32ba5748786e7801945f7d2
`991d9fa02da0dd1f843dc011376965e0c8c6c9b5`	affected	< abf2fae92cbe68945028987d498cc72f8f0e23a8
`991d9fa02da0dd1f843dc011376965e0c8c6c9b5`	affected	< 5efb1a7734ed4035fa4fdc3716bdb84621f27cf6
`991d9fa02da0dd1f843dc011376965e0c8c6c9b5`	affected	< 3dc9ae1029320d77472c44965e572f176949cd63
`991d9fa02da0dd1f843dc011376965e0c8c6c9b5`	affected	< b5f9a31c51cbb374a1713c3494f8660ab070f035
`991d9fa02da0dd1f843dc011376965e0c8c6c9b5`	affected	< 7f76245960a332f39b08cc556e675d1765dc5bbb
`991d9fa02da0dd1f843dc011376965e0c8c6c9b5`	affected	< 9f1a0d27586ceab055e6b050e3731ce3c6b2c4f0
`991d9fa02da0dd1f843dc011376965e0c8c6c9b5`	affected	< 5bcd4d3058ebaf46ad2e163829d87dd4870c7a45

Linux

affected

Version	Status	Constraints
`3.2`	affected	—
`0`	unaffected	< 3.2
`5.10.261`	unaffected	≤ 5.10.*
`5.15.212`	unaffected	≤ 5.15.*
`6.1.178`	unaffected	≤ 6.1.*
`6.6.145`	unaffected	≤ 6.6.*
`6.12.97`	unaffected	≤ 6.12.*
`6.18.40`	unaffected	≤ 6.18.*
`7.1.5`	unaffected	≤ 7.1.*
`7.2-rc3`	unaffected	≤ *

No data.

Vendor Product Confidence Versions

Linux

Linux Kernel

99%

Version	Status	Scheme	Platform
`[991d9fa02da0dd1f843dc011376965e0c8c6c9b5,4af993468193cf4cd32ba5748786e7801945f7d2)`	affected	code_commit	—
`[991d9fa02da0dd1f843dc011376965e0c8c6c9b5,abf2fae92cbe68945028987d498cc72f8f0e23a8)`	affected	code_commit	—
`[991d9fa02da0dd1f843dc011376965e0c8c6c9b5,5efb1a7734ed4035fa4fdc3716bdb84621f27cf6)`	affected	code_commit	—
`[991d9fa02da0dd1f843dc011376965e0c8c6c9b5,3dc9ae1029320d77472c44965e572f176949cd63)`	affected	code_commit	—
`[991d9fa02da0dd1f843dc011376965e0c8c6c9b5,b5f9a31c51cbb374a1713c3494f8660ab070f035)`	affected	code_commit	—
`[991d9fa02da0dd1f843dc011376965e0c8c6c9b5,7f76245960a332f39b08cc556e675d1765dc5bbb)`	affected	code_commit	—
`[991d9fa02da0dd1f843dc011376965e0c8c6c9b5,9f1a0d27586ceab055e6b050e3731ce3c6b2c4f0)`	affected	code_commit	—
`[991d9fa02da0dd1f843dc011376965e0c8c6c9b5,5bcd4d3058ebaf46ad2e163829d87dd4870c7a45)`	affected	code_commit	—

Linux

Linux Kernel

99%

Version	Status	Scheme	Platform
`3.2`	affected	generic	—
`[0,3.2)`	unaffected	generic	—
`[5.10.261,5.11.0]`	unaffected	semver	—
`[5.15.212,5.16.0]`	unaffected	semver	—
`[6.1.178,6.2.0]`	unaffected	semver	—
`[6.6.145,6.7.0]`	unaffected	semver	—
`[6.12.97,6.13.0]`	unaffected	semver	—
`[6.18.40,6.19.0]`	unaffected	semver	—
`[7.1.5,7.2.0]`	unaffected	semver	—
`[7.2-rc3,*]`	unaffected	generic	—

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Remediation

No vendor fix or workaround currently provided.

Additional remediation guidance may be available on OpenCVE Cloud.

Tracking

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Advisories

No advisories yet.

No CVSS v4.0

No CVSS v3.1

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

The EPSS score is 0.0021.

Key SSVC decision points have not yet been added.

References

Link	Providers
https://git.kernel.org/stable/c/3dc9ae1029320d77472c44965e572f176949cd63
https://git.kernel.org/stable/c/4af993468193cf4cd32ba5748786e7801945f7d2
https://git.kernel.org/stable/c/5bcd4d3058ebaf46ad2e163829d87dd4870c7a45
https://git.kernel.org/stable/c/5efb1a7734ed4035fa4fdc3716bdb84621f27cf6
https://git.kernel.org/stable/c/7f76245960a332f39b08cc556e675d1765dc5bbb
https://git.kernel.org/stable/c/9f1a0d27586ceab055e6b050e3731ce3c6b2c4f0
https://git.kernel.org/stable/c/abf2fae92cbe68945028987d498cc72f8f0e23a8
https://git.kernel.org/stable/c/b5f9a31c51cbb374a1713c3494f8660ab070f035

History

Sat, 15 Aug 2026 09:15:00 +0000

Type	Values Removed	Values Added
Weaknesses		CWE-422

Sat, 15 Aug 2026 06:00:00 +0000

Type	Values Removed	Values Added
Description		In the Linux kernel, the following vulnerability has been resolved: dm thin metadata: fix metadata snapshot consistency on commit failure __reserve_metadata_snap() and __release_metadata_snap() modify the superblock's held_root directly in the block_manager's buffer. If the subsequent metadata commit fails, the held_root gets flushed to disk through the abort_transaction path, resulting in inconsistent metadata. Reproducer 1: __reserve_metadata_snap() 1. Create a 2 MiB metadata device and make the region after the 14th block inaccessible, to trigger metadata commit failure in the subsequent reserve_metadata_snap operation. The 14th block will be the shadow destination for the index block. dmsetup create tmeta --table "0 112 linear /dev/sdc 0 112 3984 error" 2. Create a 16 MiB thin-pool dmsetup create tdata --table "0 32768 zero" dd if=/dev/zero of=/dev/mapper/tmeta bs=4k count=1 dmsetup create tpool --table "0 32768 thin-pool /dev/mapper/tmeta \ /dev/mapper/tdata 128 0 1 skip_block_zeroing" 3. Take a metadata snapshot to trigger metadata commit failure and transaction abort. However, the held_root is written to disk, breaking metadata consistency. dmsetup message tpool 0 "reserve_metadata_snap" thin_check v1.2.2 result: Bad reference count for metadata block 6. Expected 2, but space map contains 1. Bad reference count for metadata block 7. Expected 2, but space map contains 1. Bad reference count for metadata block 13. Expected 1, but space map contains 0. Reproducer 2: __release_metadata_snap() 1. Create a 2 MiB metadata device and make the region after the 16th block inaccessible, to trigger metadata commit failure in the subsequent release_metadata_snap operation. The 16th block will be the shadow destination for the index block. dmsetup create tmeta --table "0 128 linear /dev/sdc 0 128 3968 error" 2. Create a 16 MiB thin-pool dmsetup create tdata --table "0 32768 zero" dd if=/dev/zero of=/dev/mapper/tmeta bs=4k count=1 dmsetup create tpool --table "0 32768 thin-pool /dev/mapper/tmeta \ /dev/mapper/tdata 128 0 1 skip_block_zeroing" 3. Reserve then release the metadata snapshot, to trigger metadata commit failure and transaction abort. The held_root gets removed from the on-disk superblock, causing inconsistent metadata. dmsetup message tpool 0 "reserve_metadata_snap" dmsetup message tpool 0 "release_metadata_snap" thin_check v1.2.2 result: Bad reference count for metadata block 6. Expected 1, but space map contains 2. Bad reference count for metadata block 7. Expected 1, but space map contains 2. 1 metadata blocks have leaked. Fix by deferring the held_root update to commit time. Additionally, move the existing-snapshot check in __reserve_metadata_snap before the shadow operation to avoid unnecessary work. In __release_metadata_snap, clear pmd->held_root before btree deletion so partial failure leaks blocks rather than leaving a stale reference, and unlock the snapshot block before decrementing its refcount.
Title		dm thin metadata: fix metadata snapshot consistency on commit failure
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/3dc9ae1029320d77472c44965e572f176949cd63 https://git.kernel.org/stable/c/4af993468193cf4cd32ba5748786e7801945f7d2 https://git.kernel.org/stable/c/5bcd4d3058ebaf46ad2e163829d87dd4870c7a45 https://git.kernel.org/stable/c/5efb1a7734ed4035fa4fdc3716bdb84621f27cf6 https://git.kernel.org/stable/c/7f76245960a332f39b08cc556e675d1765dc5bbb https://git.kernel.org/stable/c/9f1a0d27586ceab055e6b050e3731ce3c6b2c4f0 https://git.kernel.org/stable/c/abf2fae92cbe68945028987d498cc72f8f0e23a8 https://git.kernel.org/stable/c/b5f9a31c51cbb374a1713c3494f8660ab070f035

Subscriptions

Linux Linux Kernel

MITRE

Status: PUBLISHED

Assigner: Linux

Published: 2026-08-15T05:52:50.321Z

Updated: 2026-08-15T05:52:50.321Z

Reserved: 2026-08-09T03:40:39.906Z

Link: CVE-2026-72108

Vulnrichment

No data.

NVD

Status : Received

Published: 2026-08-15T06:21:25.047

Modified: 2026-08-15T06:21:25.047

Link: CVE-2026-72108

Redhat

No data.

OpenCVE Enrichment

Updated: 2026-08-15T18:15:03Z

Weaknesses

CWE-422
Unprotected Windows Messaging Channel ('Shatter')

Tracking

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