CVE-2025-68823

Local service hang via ublk mutex reentry

Published Jan 13, 2026 · Updated Jan 13, 2026

Improper locking in the Linux Kernel ublk driver allows local users to hang ublk I/O while a partition table is read. During __ublk_complete_rq(), request completion can run fput() as task work and reenter blkdev_release(), which reacquires disk->open_mutex already held by bdev_open(). Triggering the cycle requires an opened ublk block device, partition-table read I/O, and a completion callback that closes its descriptor; the ublk server then cannot progress.

CVSS severity5.5
Medium
EPSS probability0.13%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper locking in the Linux Kernel ublk driver allows local users to hang ublk I/O while a partition table is read. During __ublk_complete_rq(), request completion can run fput() as task work and reenter blkdev_release(), which reacquires disk->open_mutex already held by bdev_open(). Triggering the cycle requires an opened ublk block device, partition-table read I/O, and a completion callback that closes its descriptor; the ublk server then cannot progress.

The record

CVE
CVE-2025-68823
Published
Jan 13, 2026
Updated
Jan 13, 2026
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
CWE-667, T1499.004
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Jan 13, 2026CVE publishedPublication date reported by the CVE source.
  2. Jan 13, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=6.0
  2. Affected versionversion=71f28f3136aff5890cd56de78abc673f8393cad9 <0460e09a614291f06c008443f47393c37b7358e7
  3. Affected versionversion=71f28f3136aff5890cd56de78abc673f8393cad9 <c258f5c4502c9667bccf5d76fa731ab9c96687c1

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linux Kernelversion=6.0; version=71f28f3136aff5890cd56de78abc673f8393cad9 <0460e09a614291f06c008443f47393c37b7358e7; version=71f28f3136aff5890cd56de78abc673f8393cad9 <c258f5c4502c9667bccf5d76fa731ab9c96687c1

Published CVSS scores

5.5NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-667Improper Locking
T1499.004Endpoint Denial of Service: Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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