# CVE-2025-21832: block: don't revert iter for -EIOCBQUEUED

> A logic error in the Linux kernel block layer can trigger a warning and potential denial of service when handling queued I/O operations.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **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:** 6 Mar 2025
- **Updated:** 15 Oct 2026
- **Also known as:** BELL-CVE-2025-21832, DEBIAN-CVE-2025-21832, GHSA-cwfx-m26m-rjc8, ROOT-OS-UBUNTU-2204-CVE-2025-21832, ROOT-OS-UBUNTU-2404-CVE-2025-21832, UBUNTU-CVE-2025-21832

## What is CVE-2025-21832?

CVE-2025-21832 is a high-severity denial of service vulnerability in Linux kernel, published on 6 Mar 2025. 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:

block: don't revert iter for -EIOCBQUEUED

blkdev_read_iter() has a few odd checks, like gating the position and
count adjustment on whether or not the result is bigger-than-or-equal to
zero (where bigger than makes more sense), and not checking the return
value of blkdev_direct_IO() before doing an iov_iter_revert(). The
latter can lead to attempting to revert with a negative value, which
when passed to iov_iter_revert() as an unsigned value will lead to
throwing a WARN_ON() because unroll is bigger than MAX_RW_COUNT.

Be sane and don't revert for -EIOCBQUEUED, like what is done in other
spots.

## Which versions are affected by CVE-2025-21832?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2025-21832?

Apply the vendor's patch.

## Is CVE-2025-21832 being exploited?

There is no known exploitation of CVE-2025-21832 in the wild and no public exploit code.

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-21832 and fix it if it is affected.

What it is: CVE-2025-21832 is a high-severity denial of service vulnerability in Linux kernel, published on 6 Mar 2025. 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-2025-21832 in the wild and no public exploit code.

Affected product: Linux kernel. 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-2025-21832/ (Markdown: https://insights.sbomify.com/CVE-2025-21832/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-21832
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-21832
- OSV: https://osv.dev/vulnerability/CVE-2025-21832

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-21832/
Summaries are generated and may contain mistakes; the official description above is the record.