# CVE-2025-68257: comedi: check device's attached status in compat ioctls

> A local attacker can trigger a kernel crash via compat ioctls on unconfigured comedi devices, causing denial of service.

- **Severity:** Not scored
- **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:** 16 Dec 2025
- **Updated:** 11 May 2026
- **Also known as:** BELL-CVE-2025-68257, DEBIAN-CVE-2025-68257, GHSA-q3m2-j43g-7966, ROOT-OS-DEBIAN-11-CVE-2025-68257, ROOT-OS-DEBIAN-12-CVE-2025-68257, ROOT-OS-DEBIAN-13-CVE-2025-68257, ROOT-OS-UBUNTU-2204-CVE-2025-68257, ROOT-OS-UBUNTU-2404-CVE-2025-68257, UBUNTU-CVE-2025-68257

## What is CVE-2025-68257?

CVE-2025-68257 is a vulnerability in Linux, published on 16 Dec 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:

comedi: check device's attached status in compat ioctls

Syzbot identified an issue [1] that crashes kernel, seemingly due to
unexistent callback dev->get_valid_routes(). By all means, this should
not occur as said callback must always be set to
get_zero_valid_routes() in __comedi_device_postconfig().

As the crash seems to appear exclusively in i386 kernels, at least,
judging from [1] reports, the blame lies with compat versions
of standard IOCTL handlers. Several of them are modified and
do not use comedi_unlocked_ioctl(). While functionality of these
ioctls essentially copy their original versions, they do not
have required sanity check for device's attached status. This,
in turn, leads to a possibility of calling select IOCTLs on a
device that has not been properly setup, even via COMEDI_DEVCONFIG.

Doing so on unconfigured devices means that several crucial steps
are missed, for instance, specifying dev->get_valid_routes()
callback.

Fix this somewhat crudely by ensuring device's attached status before
performing any ioctls, improving logic consistency between modern
and compat functions.

[1] Syzbot report:
BUG: kernel NULL pointer dereference, address: 0000000000000000
...
CR2: ffffffffffffffd6 CR3: 000000006c717000 CR4: 0000000000352ef0
Call Trace:
 <TASK>
 get_valid_routes drivers/comedi/comedi_fops.c:1322 [inline]
 parse_insn+0x78c/0x1970 drivers/comedi/comedi_fops.c:1401
 do_insnlist_ioctl+0x272/0x700 drivers/comedi/comedi_fops.c:1594
 compat_insnlist drivers/comedi/comedi_fops.c:3208 [inline]
 comedi_compat_ioctl+0x810/0x990 drivers/comedi/comedi_fops.c:3273
 __do_compat_sys_ioctl fs/ioctl.c:695 [inline]
 __se_compat_sys_ioctl fs/ioctl.c:638 [inline]
 __ia32_compat_sys_ioctl+0x242/0x370 fs/ioctl.c:638
 do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:83 [inline]
...

## Which versions are affected by CVE-2025-68257?


## How do I fix CVE-2025-68257?

Apply the vendor's patch.

## Is CVE-2025-68257 being exploited?

There is no known exploitation of CVE-2025-68257 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-68257 and fix it if it is affected.

What it is: CVE-2025-68257 is a vulnerability in Linux, published on 16 Dec 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-2025-68257 in the wild and no public exploit code.

Affected product: Linux. 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-2025-68257/ (Markdown: https://insights.sbomify.com/CVE-2025-68257/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-68257
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-68257
- OSV: https://osv.dev/vulnerability/CVE-2025-68257

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-68257/
Summaries are generated and may contain mistakes; the official description above is the record.