CVE-2025-68823

CVE-2025-68823 is a medium-severity vulnerability in Linux Linux Kernel with a CVSS 3.x base score of 5.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-667.

Key facts

Description

In the Linux kernel, the following vulnerability has been resolved: ublk: fix deadlock when reading partition table When one process(such as udev) opens ublk block device (e.g., to read the partition table via bdev_open()), a deadlock[1] can occur: 1. bdev_open() grabs disk->open_mutex 2. The process issues read I/O to ublk backend to read partition table 3. In __ublk_complete_rq(), blk_update_request() or blk_mq_end_request() runs bio->bi_end_io() callbacks 4. If this triggers fput() on file descriptor of ublk block device, the work may be deferred to current task's task work (see fput() implementation) 5. This eventually calls blkdev_release() from the same context 6. blkdev_release() tries to grab disk->open_mutex again 7. Deadlock: same task waiting for a mutex it already holds The fix is to run blk_update_request() and blk_mq_end_request() with bottom halves disabled. This forces blkdev_release() to run in kernel work-queue context instead of current task work context, and allows ublk server to make forward progress, and avoids the deadlock. [axboe: rewrite comment in ublk]

Frequently asked questions

What is CVE-2025-68823?
In the Linux kernel, the following vulnerability has been resolved: ublk: fix deadlock when reading partition table When one process(such as udev) opens ublk block device (e.g., to read the partition table via bdev_open()), a deadlock[1] can occur: 1. bdev_open() grabs disk->open_mutex 2. The process issues read I/O to ublk backend to read partition table 3. In __ublk_complete_rq(), blk_update_request() or blk_mq_end_request() runs bio->bi_end_io() callbacks 4. If this triggers fput() on file descriptor of ublk block device, the work may be deferred to current task's task work (see fput() implementation) 5. This eventually calls blkdev_release() from the same context 6. blkdev_release() tries to grab disk->open_mutex again 7. Deadlock: same task waiting for a mutex it already holds The fix is to run blk_update_request() and blk_mq_end_request() with bottom halves disabled. This forces blkdev_release() to run in kernel work-queue context instead of current task work context, and allows ublk server to make forward progress, and avoids the deadlock. [axboe: rewrite comment in ublk]
How severe is CVE-2025-68823?
CVE-2025-68823 has a CVSS 3.x base score of 5.5, rated medium severity. It is exploitable over local access with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2025-68823 being actively exploited?
It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (2nd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2025-68823?
CVE-2025-68823 primarily affects Linux Linux Kernel. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2025-68823?
Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2025-68823 have an EU (EUVD) identifier?
Yes. CVE-2025-68823 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-2278.
When was CVE-2025-68823 published?
CVE-2025-68823 was published on 2026-01-13 and last updated on 2026-06-17.

References

Affected products (2)

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