# CVE-2026-98723: nvmet: copy the hostid into the ctrl before creating PR pc_refs

> A logic error in Linux kernel NVMe target allows hosts to bypass reservation abort mechanisms, leaving victim I/O active during preemption.

- **Severity:** Not scored
- **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:** 18 Oct 2026
- **Updated:** 19 Oct 2026
- **Also known as:** BELL-CVE-2026-98723, DEBIAN-CVE-2026-98723, GHSA-hpxm-6496-49xp, UBUNTU-CVE-2026-98723

## What is CVE-2026-98723?

CVE-2026-98723 is a vulnerability in Linux, published on 18 Oct 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:

nvmet: copy the hostid into the ctrl before creating PR pc_refs

Commit 6202783184bf ("nvmet: Improve nvmet_alloc_ctrl() interface and
implementation") added a second uuid_copy() of args->hostid near the end
of nvmet_alloc_ctrl(), and commit 7b658153f1b8 ("nvmet: Remove duplicate
uuid_copy") removed the original copy that sat before
nvmet_ctrl_init_pr() instead of the new one.

Since then nvmet_ctrl_init_pr() snapshots ctrl->hostid into the
per-controller per-namespace reservation refs while the uuid_copy()
from the connect data runs later, after the controller is published.
The ctrl is allocated with kzalloc(), so every pc_ref created on this
path stores the nil UUID.

pc_ref->hostid has a single consumer: nvmet_pr_set_ctrl_to_abort()
matches it against the preempted registrant's hostid to kill and drain
the victim's in-flight I/O for Preempt and Abort.  The match can never
hit with the nil UUID, so whenever a namespace with reservations
enabled exists before a host connects, which includes every reconnect,
Preempt and Abort silently degrades into a plain Preempt: the
preempting host sees success while the victim's in-flight I/O is still
in the air.

Copy the hostid where the rest of the connect data is consumed, before
the controller is published and before nvmet_ctrl_init_pr() takes its
snapshot.

## Which versions are affected by CVE-2026-98723?


## How do I fix CVE-2026-98723?

Apply the vendor's patch.

## Is CVE-2026-98723 being exploited?

There is no known exploitation of CVE-2026-98723 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98723 and fix it if it is affected.

What it is: CVE-2026-98723 is a vulnerability in Linux, published on 18 Oct 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-2026-98723 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-2026-98723/ (Markdown: https://insights.sbomify.com/CVE-2026-98723/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98723
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98723
- OSV: https://osv.dev/vulnerability/CVE-2026-98723

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98723/
Summaries are generated and may contain mistakes; the official description above is the record.