# CVE-2026-90095: fuse: Fix the condition to enable over-io-uring

> A race condition in the Linux kernel FUSE io-uring implementation can cause deadlocks, leading to denial of service for local users.

- **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:** 17 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** BELL-CVE-2026-90095, DEBIAN-CVE-2026-90095, GHSA-f6c3-623p-967p, UBUNTU-CVE-2026-90095

## What is CVE-2026-90095?

CVE-2026-90095 is a vulnerability in Linux, published on 17 Sep 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:

fuse: Fix the condition to enable over-io-uring

The existing condition in fuse_uring_cmd() is there only to avoid
disabling io-uring for connections that already run with it, missing
was a condition to refuse any IORING_OP_URING_CMD if the
connection/channel didn't get enabled because of missing FUSE_INIT
reply flag FUSE_OVER_IO_URING. Without the reply flag the barrier in
fuse_uring_ready() doesn't work and IO could already be going on and
cause deadlock states (at a minimum one between fch->bg_lock and
queue->lock).

The change itself is trivial, but brings behavior change,
FUSE_OVER_IO_URING has to be set in the FUSE_INIT_REPLY by fuse servers
to accept any IORING_OP_URING_CMD. Libfuse does that and the only
non-libfuse implementation I found (fractal-fuse) also does it.
Qemu patches for fuse-io-uring are not merged yet, as far as I know.

Moved up is the smp_load_acquire(&fch->initialized) check, as a
fuse-server implementation might try to setup io-uring before FUSE_INIT
is processed and might have gotten -EOPNOTSUPP instead of -EAGAIN.

Also fixed is a stale comment that explains the handling of the
FUSE_OVER_IO_URING flag in early RFC versions.

If there should be a report from any library or application we
probably need to revert this commit.

## Which versions are affected by CVE-2026-90095?


## How do I fix CVE-2026-90095?

Apply the vendor's patch.

## Is CVE-2026-90095 being exploited?

There is no known exploitation of CVE-2026-90095 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-90095 and fix it if it is affected.

What it is: CVE-2026-90095 is a vulnerability in Linux, published on 17 Sep 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-2026-90095 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-2026-90095/ (Markdown: https://insights.sbomify.com/CVE-2026-90095/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-90095
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-90095
- OSV: https://osv.dev/vulnerability/CVE-2026-90095

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-90095/
Summaries are generated and may contain mistakes; the official description above is the record.