# CVE-2025-21804: PCI: rcar-ep: Fix incorrect variable used when calling devm_request_mem_region()

> A bug in the Linux kernel PCI driver can cause a system crash due to undefined behavior when handling memory region names.

- **Severity:** High 7.1 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/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:** 5 Aug 2026
- **Also known as:** BELL-CVE-2025-21804, DEBIAN-CVE-2025-21804, GHSA-8w2r-337g-j83r, ROOT-OS-UBUNTU-2404-CVE-2025-21804, UBUNTU-CVE-2025-21804

## What is CVE-2025-21804?

CVE-2025-21804 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:

PCI: rcar-ep: Fix incorrect variable used when calling devm_request_mem_region()

The rcar_pcie_parse_outbound_ranges() uses the devm_request_mem_region()
macro to request a needed resource. A string variable that lives on the
stack is then used to store a dynamically computed resource name, which
is then passed on as one of the macro arguments. This can lead to
undefined behavior.

Depending on the current contents of the memory, the manifestations of
errors may vary. One possible output may be as follows:

  $ cat /proc/iomem
  30000000-37ffffff :
  38000000-3fffffff :

Sometimes, garbage may appear after the colon.

In very rare cases, if no NULL-terminator is found in memory, the system
might crash because the string iterator will overrun which can lead to
access of unmapped memory above the stack.

Thus, fix this by replacing outbound_name with the name of the previously
requested resource. With the changes applied, the output will be as
follows:

  $ cat /proc/iomem
  30000000-37ffffff : memory2
  38000000-3fffffff : memory3

[kwilczynski: commit log]

Weakness: CWE-476 (NULL Pointer Dereference)

## Which versions are affected by CVE-2025-21804?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2025-21804?

Apply the vendor's patch.

## Is CVE-2025-21804 being exploited?

There is no known exploitation of CVE-2025-21804 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-2025-21804 and fix it if it is affected.

What it is: CVE-2025-21804 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-2025-21804 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-2025-21804/ (Markdown: https://insights.sbomify.com/CVE-2025-21804/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-21804
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-21804
- OSV: https://osv.dev/vulnerability/CVE-2025-21804

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-21804/
Summaries are generated and may contain mistakes; the official description above is the record.