# CVE-2026-74392: dm: limit target bio polling to one shot

> A local attacker can trigger an RCU CPU stall in the Linux kernel device mapper by exploiting io_uring IOPOLL, causing a 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:** 15 Aug 2026
- **Updated:** 17 Aug 2026
- **Also known as:** DEBIAN-CVE-2026-74392, GHSA-mp22-m63x-2wq5, UBUNTU-CVE-2026-74392

## What is CVE-2026-74392?

CVE-2026-74392 is a denial of service vulnerability in Linux, published on 15 Aug 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:

dm: limit target bio polling to one shot

dm_poll_bio() is the ->poll_bio() callback for a stacked dm device.
The caller only knows about the dm queue, so it may decide to do a
spinning poll if it thinks a single queue is being polled. Passing those
flags unchanged to the mapped clone lets blk_mq_poll() spin on a target
queue from inside dm_poll_bio().

With io_uring IOPOLL on a dm-stripe target this can keep a task in

  dm_poll_bio() -> bio_poll() -> blk_mq_poll()

long enough to trigger an RCU CPU stall, before io_uring gets back to
io_iopoll_check() and its need_resched() check.

Keep dm's ->poll_bio() bounded by forcing one-shot polling for target
bios. The caller can invoke dm_poll_bio() again if it wants to keep
polling, and it also gets a chance to reap completions or reschedule
between passes.

## Which versions are affected by CVE-2026-74392?


## How do I fix CVE-2026-74392?

Apply the vendor's patch.

## Is CVE-2026-74392 being exploited?

There is no known exploitation of CVE-2026-74392 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-74392 and fix it if it is affected.

What it is: CVE-2026-74392 is a denial of service vulnerability in Linux, published on 15 Aug 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-2026-74392 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-2026-74392/ (Markdown: https://insights.sbomify.com/CVE-2026-74392/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-74392
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-74392
- OSV: https://osv.dev/vulnerability/CVE-2026-74392

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-74392/
Summaries are generated and may contain mistakes; the official description above is the record.