# CVE-2025-21738: ata: libata-sff: Ensure that we cannot write outside the allocated buffer

> A missing bounds check in the Linux kernel's libata-sff driver allows out-of-bounds writes, potentially leading to memory corruption and privilege escalation.

- **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:** AZL-68973, BELL-CVE-2025-21738, DEBIAN-CVE-2025-21738, GHSA-f4r5-w3wm-c5g6, ROOT-OS-DEBIAN-11-CVE-2025-21738, ROOT-OS-UBUNTU-2204-CVE-2025-21738, ROOT-OS-UBUNTU-2404-CVE-2025-21738, SUSE-SU-2026:1060-1, UBUNTU-CVE-2025-21738

## What is CVE-2025-21738?

CVE-2025-21738 is a high-severity memory corruption 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:

ata: libata-sff: Ensure that we cannot write outside the allocated buffer

reveliofuzzing reported that a SCSI_IOCTL_SEND_COMMAND ioctl with out_len
set to 0xd42, SCSI command set to ATA_16 PASS-THROUGH, ATA command set to
ATA_NOP, and protocol set to ATA_PROT_PIO, can cause ata_pio_sector() to
write outside the allocated buffer, overwriting random memory.

While a ATA device is supposed to abort a ATA_NOP command, there does seem
to be a bug either in libata-sff or QEMU, where either this status is not
set, or the status is cleared before read by ata_sff_hsm_move().
Anyway, that is most likely a separate bug.

Looking at __atapi_pio_bytes(), it already has a safety check to ensure
that __atapi_pio_bytes() cannot write outside the allocated buffer.

Add a similar check to ata_pio_sector(), such that also ata_pio_sector()
cannot write outside the allocated buffer.

## Which versions are affected by CVE-2025-21738?

It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `kernel-livepatch-SLE15-SP5_Update_35` | SUSE:Linux Enterprise Live Patching 15 SP5 | All versions | 2-150500.2.1 |

Products: Linux kernel.

## How do I fix CVE-2025-21738?

Apply the vendor's patch.

## Is CVE-2025-21738 being exploited?

There is no known exploitation of CVE-2025-21738 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-2025-21738 and fix it if it is affected.

What it is: CVE-2025-21738 is a high-severity memory corruption 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-2025-21738 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-2025-21738/ (Markdown: https://insights.sbomify.com/CVE-2025-21738/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-21738
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-21738
- OSV: https://osv.dev/vulnerability/CVE-2025-21738

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-21738/
Summaries are generated and may contain mistakes; the official description above is the record.