CVE-2025-68823 ublk: fix deadlock when reading partition table
A deadlock in the Linux kernel ublk driver can cause a denial of service when reading partition tables.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2025-68823?
CVE-2025-68823 is a medium-severity vulnerability in Linux kernel, published on 13 Jan 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official 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]
Weakness: CWE-667
Which versions are affected by CVE-2025-68823?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2025-68823?
Apply the vendor's patch.
Is CVE-2025-68823 being exploited?
There is no known exploitation of CVE-2025-68823 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2025-68823, DEBIAN-CVE-2025-68823, GHSA-72w6-32c7-vf7p, ROOT-OS-DEBIAN-12-CVE-2025-68823, ROOT-OS-DEBIAN-13-CVE-2025-68823, ROOT-OS-UBUNTU-2404-CVE-2025-68823 and 1 more.