# 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.

- **Severity:** Medium 5.5 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H`)
- **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:** Yes
- **Published:** 13 Jan 2026
- **Updated:** 1 Jun 2026
- **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, UBUNTU-CVE-2025-68823

## 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 (Improper Locking)

## Which versions are affected by CVE-2025-68823?

It affects 1 product.


Products: 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

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-68823 and fix it if it is affected.

What it is: 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.
Exploitation: There is no known exploitation of CVE-2025-68823 in the wild and no public exploit code.

Affected product: Linux kernel. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2025-68823/ (Markdown: https://insights.sbomify.com/CVE-2025-68823/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-68823
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-68823
- OSV: https://osv.dev/vulnerability/CVE-2025-68823

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-68823/
Summaries are generated and may contain mistakes; the official description above is the record.