# CVE-2026-98820: blk-mq: set RQF_USE_SCHED when the operation is known

> A Linux kernel bug in blk-mq allows local attackers to cause a denial of service by stalling the I/O queue through scheduler token leaks.

- **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:** 18 Oct 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-109250, BELL-CVE-2026-98820, DEBIAN-CVE-2026-98820, GHSA-95f6-3pp2-9382, UBUNTU-CVE-2026-98820

## What is CVE-2026-98820?

CVE-2026-98820 is a denial of service 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:

blk-mq: set RQF_USE_SCHED when the operation is known

The cached requests are allocated for one operation but can be handed
out for another. A passthrough command has RQF_USE_SCHED cleared, so
using those flags for a subsequent read/write bio will insert it into
the scheduler without ->prepare_request() and frees it without
->finish_request(). For kyber, this leaks the domain token acquired at
dispatch and stalls the queue.

Don't set RQF_USE_SCHED based on the first operation the batch happened
to be allocated for. Instead, set it after the request is claimed by an
operation. Introduce a helper function, blk_mq_rq_late_init() for this,
and absorb blk_mq_rq_time_init() since the two run together.

## Which versions are affected by CVE-2026-98820?


## How do I fix CVE-2026-98820?

Apply the vendor's patch.

## Is CVE-2026-98820 being exploited?

There is no known exploitation of CVE-2026-98820 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98820 and fix it if it is affected.

What it is: CVE-2026-98820 is a denial of service 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-2026-98820 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-2026-98820/ (Markdown: https://insights.sbomify.com/CVE-2026-98820/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98820
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98820
- OSV: https://osv.dev/vulnerability/CVE-2026-98820

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98820/
Summaries are generated and may contain mistakes; the official description above is the record.