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Unity Linux 20.1050a Security Update: kernel (UTSA-2026-104554)
high Nessus Plugin ID 339556
Synopsis
The Unity Linux host is missing one or more security updates.Description
The Unity Linux 20 host has a package installed that is affected by a vulnerability as referenced in the UTSA-2026-104554 advisory.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.
Tenable has extracted the preceding description block directly from the Unity Linux security advisory.
Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.
Solution
Update the affected kernel package.See Also
https://nvd.nist.gov/vuln/detail/CVE-2026-72108
Plugin Details
Severity: High
ID: 339556
File Name: unity_linux_UTSA-2026-104554.nasl
Version: 1.1
Type: Local
Published: 8/26/2026
Updated: 8/26/2026
Supported Sensors: Nessus
Risk Information
VPR
Risk Factor: Medium
Score: 4.9
Percentile: 58.13
CVSS v2
Risk Factor: Medium
Base Score: 6.8
Temporal Score: 5
Vector: CVSS2#AV:L/AC:L/Au:S/C:C/I:C/A:C
CVSS Score Source: CVE-2026-72108
CVSS v3
Risk Factor: High
Base Score: 7.8
Temporal Score: 6.8
Vector: CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Temporal Vector: CVSS:3.0/E:U/RL:O/RC:C
Vulnerability Information
Required KB Items: Host/local_checks_enabled, Host/cpu, Host/UOS-Server/release, Host/UOS-Server/rpm-list
Exploit Ease: No known exploits are available
Patch Publication Date: 8/25/2026
Vulnerability Publication Date: 8/11/2026
Reference Information
CVE: CVE-2026-72108