# CVE-2025-68258: comedi: multiq3: sanitize config options in multiq3_attach()

> A local attacker can cause a denial of service in the Linux kernel comedi multiq3 driver by providing excessive configuration options during device attachment.

- **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-2025-68258, DEBIAN-CVE-2025-68258, GHSA-p2q7-w28w-9654, ROOT-OS-DEBIAN-11-CVE-2025-68258, ROOT-OS-DEBIAN-12-CVE-2025-68258, ROOT-OS-DEBIAN-13-CVE-2025-68258, ROOT-OS-UBUNTU-2204-CVE-2025-68258, ROOT-OS-UBUNTU-2404-CVE-2025-68258, UBUNTU-CVE-2025-68258

## What is CVE-2025-68258?

CVE-2025-68258 is a denial of service 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: multiq3: sanitize config options in multiq3_attach()

Syzbot identified an issue [1] in multiq3_attach() that induces a
task timeout due to open() or COMEDI_DEVCONFIG ioctl operations,
specifically, in the case of multiq3 driver.

This problem arose when syzkaller managed to craft weird configuration
options used to specify the number of channels in encoder subdevice.
If a particularly great number is passed to s->n_chan in
multiq3_attach() via it->options[2], then multiple calls to
multiq3_encoder_reset() at the end of driver-specific attach() method
will be running for minutes, thus blocking tasks and affected devices
as well.

While this issue is most likely not too dangerous for real-life
devices, it still makes sense to sanitize configuration inputs. Enable
a sensible limit on the number of encoder chips (4 chips max, each
with 2 channels) to stop this behaviour from manifesting.

[1] Syzbot crash:
INFO: task syz.2.19:6067 blocked for more than 143 seconds.
...
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5254 [inline]
 __schedule+0x17c4/0x4d60 kernel/sched/core.c:6862
 __schedule_loop kernel/sched/core.c:6944 [inline]
 schedule+0x165/0x360 kernel/sched/core.c:6959
 schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:7016
 __mutex_lock_common kernel/locking/mutex.c:676 [inline]
 __mutex_lock+0x7e6/0x1350 kernel/locking/mutex.c:760
 comedi_open+0xc0/0x590 drivers/comedi/comedi_fops.c:2868
 chrdev_open+0x4cc/0x5e0 fs/char_dev.c:414
 do_dentry_open+0x953/0x13f0 fs/open.c:965
 vfs_open+0x3b/0x340 fs/open.c:1097
...

## Which versions are affected by CVE-2025-68258?


## How do I fix CVE-2025-68258?

Apply the vendor's patch.

## Is CVE-2025-68258 being exploited?

There is no known exploitation of CVE-2025-68258 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-68258 and fix it if it is affected.

What it is: CVE-2025-68258 is a denial of service 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-2025-68258 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-2025-68258/ (Markdown: https://insights.sbomify.com/CVE-2025-68258/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-68258
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-68258
- OSV: https://osv.dev/vulnerability/CVE-2025-68258

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-68258/
Summaries are generated and may contain mistakes; the official description above is the record.