# CVE-2026-23047: libceph: make calc_target() set t->paused, not just clear it

> A flaw in the Linux kernel Ceph client causes RBD image unmap operations to hang indefinitely, leading to a local denial of service.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 4 Feb 2026
- **Updated:** 11 May 2026
- **Also known as:** BELL-CVE-2026-23047, DEBIAN-CVE-2026-23047, GHSA-484m-2c5w-2g38, ROOT-OS-DEBIAN-11-CVE-2026-23047, ROOT-OS-DEBIAN-12-CVE-2026-23047, ROOT-OS-DEBIAN-13-CVE-2026-23047, ROOT-OS-UBUNTU-2404-CVE-2026-23047, UBUNTU-CVE-2026-23047

## What is CVE-2026-23047?

CVE-2026-23047 is a denial of service vulnerability in Linux, published on 4 Feb 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:

libceph: make calc_target() set t->paused, not just clear it

Currently calc_target() clears t->paused if the request shouldn't be
paused anymore, but doesn't ever set t->paused even though it's able to
determine when the request should be paused.  Setting t->paused is left
to __submit_request() which is fine for regular requests but doesn't
work for linger requests -- since __submit_request() doesn't operate
on linger requests, there is nowhere for lreq->t.paused to be set.
One consequence of this is that watches don't get reestablished on
paused -> unpaused transitions in cases where requests have been paused
long enough for the (paused) unwatch request to time out and for the
subsequent (re)watch request to enter the paused state.  On top of the
watch not getting reestablished, rbd_reregister_watch() gets stuck with
rbd_dev->watch_mutex held:

  rbd_register_watch
    __rbd_register_watch
      ceph_osdc_watch
        linger_reg_commit_wait

It's waiting for lreq->reg_commit_wait to be completed, but for that to
happen the respective request needs to end up on need_resend_linger list
and be kicked when requests are unpaused.  There is no chance for that
if the request in question is never marked paused in the first place.

The fact that rbd_dev->watch_mutex remains taken out forever then
prevents the image from getting unmapped -- "rbd unmap" would inevitably
hang in D state on an attempt to grab the mutex.

## Which versions are affected by CVE-2026-23047?


## How do I fix CVE-2026-23047?

Apply the vendor's patch.

## Is CVE-2026-23047 being exploited?

There is no known exploitation of CVE-2026-23047 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-23047 and fix it if it is affected.

What it is: CVE-2026-23047 is a denial of service vulnerability in Linux, published on 4 Feb 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-2026-23047 in the wild and no public exploit code.

Affected product: Linux. 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-2026-23047/ (Markdown: https://insights.sbomify.com/CVE-2026-23047/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-23047
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-23047
- OSV: https://osv.dev/vulnerability/CVE-2026-23047

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-23047/
Summaries are generated and may contain mistakes; the official description above is the record.