# CVE-2025-21915: cdx: Fix possible UAF error in driver_override_show()

> A race condition in the Linux kernel CDX bus driver allows unprivileged users to trigger a use-after-free, potentially leaking kernel addresses or causing a crash.

- **Severity:** High 7.0 (`CVSS:3.1/AV:L/AC:H/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:** 1 Apr 2025
- **Updated:** 5 Aug 2026
- **Also known as:** BELL-CVE-2025-21915, DEBIAN-CVE-2025-21915, GHSA-4v94-f8pq-mj8v, ROOT-OS-UBUNTU-2204-CVE-2025-21915, ROOT-OS-UBUNTU-2404-CVE-2025-21915, UBUNTU-CVE-2025-21915

## What is CVE-2025-21915?

CVE-2025-21915 is a high-severity use after free vulnerability in Linux kernel, published on 1 Apr 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:

cdx: Fix possible UAF error in driver_override_show()

Fixed a possible UAF problem in driver_override_show() in drivers/cdx/cdx.c

This function driver_override_show() is part of DEVICE_ATTR_RW, which
includes both driver_override_show() and driver_override_store().
These functions can be executed concurrently in sysfs.

The driver_override_store() function uses driver_set_override() to
update the driver_override value, and driver_set_override() internally
locks the device (device_lock(dev)). If driver_override_show() reads
cdx_dev->driver_override without locking, it could potentially access
a freed pointer if driver_override_store() frees the string
concurrently. This could lead to printing a kernel address, which is a
security risk since DEVICE_ATTR can be read by all users.

Additionally, a similar pattern is used in drivers/amba/bus.c, as well
as many other bus drivers, where device_lock() is taken in the show
function, and it has been working without issues.

This potential bug was detected by our experimental static analysis
tool, which analyzes locking APIs and paired functions to identify
data races and atomicity violations.

Weakness: CWE-416 (Use After Free)

## Which versions are affected by CVE-2025-21915?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2025-21915?

Apply the vendor's patch.

## Is CVE-2025-21915 being exploited?

There is no known exploitation of CVE-2025-21915 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-2025-21915 and fix it if it is affected.

What it is: CVE-2025-21915 is a high-severity use after free vulnerability in Linux kernel, published on 1 Apr 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-2025-21915 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-2025-21915/ (Markdown: https://insights.sbomify.com/CVE-2025-21915/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-21915
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-21915
- OSV: https://osv.dev/vulnerability/CVE-2025-21915

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-21915/
Summaries are generated and may contain mistakes; the official description above is the record.