# CVE-2025-21724: iommufd/iova_bitmap: Fix shift-out-of-bounds in iova_bitmap_offset_to_index()

> A shift-out-of-bounds error in the Linux kernel's iommufd module can cause undefined behavior and potential denial of service.

- **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:** 27 Feb 2025
- **Updated:** 15 Oct 2026
- **Also known as:** BELL-CVE-2025-21724, DEBIAN-CVE-2025-21724, GHSA-hx7m-g669-h6j3, ROOT-OS-UBUNTU-2404-CVE-2025-21724, UBUNTU-CVE-2025-21724

## What is CVE-2025-21724?

CVE-2025-21724 is a high-severity vulnerability in Linux kernel, published on 27 Feb 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:

iommufd/iova_bitmap: Fix shift-out-of-bounds in iova_bitmap_offset_to_index()

Resolve a UBSAN shift-out-of-bounds issue in iova_bitmap_offset_to_index()
where shifting the constant "1" (of type int) by bitmap->mapped.pgshift
(an unsigned long value) could result in undefined behavior.

The constant "1" defaults to a 32-bit "int", and when "pgshift" exceeds
31 (e.g., pgshift = 63) the shift operation overflows, as the result
cannot be represented in a 32-bit type.

To resolve this, the constant is updated to "1UL", promoting it to an
unsigned long type to match the operand's type.

Weakness: CWE-787 (Out-of-bounds Write)

## Which versions are affected by CVE-2025-21724?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2025-21724?

Apply the vendor's patch.

## Is CVE-2025-21724 being exploited?

There is no known exploitation of CVE-2025-21724 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-2025-21724 and fix it if it is affected.

What it is: CVE-2025-21724 is a high-severity vulnerability in Linux kernel, published on 27 Feb 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-2025-21724 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-2025-21724/ (Markdown: https://insights.sbomify.com/CVE-2025-21724/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-21724
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-21724
- OSV: https://osv.dev/vulnerability/CVE-2025-21724

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-21724/
Summaries are generated and may contain mistakes; the official description above is the record.