# CVE-2026-68179: misc: nsm: only unlock nsm_dev on post-lock error paths

> A local attacker can trigger a kernel warning and potential instability by causing an invalid unlock of a mutex in the NSM driver via a specific ioctl call.

- **Severity:** High 8.4 (`CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 10 Aug 2026
- **Updated:** 19 Oct 2026
- **Also known as:** BELL-CVE-2026-68179, DEBIAN-CVE-2026-68179, GHSA-3jf9-7qhv-4pm6, UBUNTU-CVE-2026-68179

## What is CVE-2026-68179?

CVE-2026-68179 is a high-severity vulnerability in Linux, published on 10 Aug 2026. 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:

misc: nsm: only unlock nsm_dev on post-lock error paths

nsm_dev_ioctl() jumps to the common out label even when the initial
copy_from_user() fails before nsm->lock has been taken.  The error path
then blindly unlocks a mutex that was never acquired.

This issue was found by our static analysis tool and then manually
reviewed against the current tree.

The grounded PoC kept the miscdevice ioctl entry and the pre-lock
copy_from_user(&raw, argp, _IOC_SIZE(cmd)) failure path by issuing
NSM_IOCTL_RAW with an invalid user pointer.  That failure reaches the
shared out label before mutex_lock(&nsm->lock).  Lockdep reported:

  WARNING: bad unlock balance detected!
  exploit/193 is trying to release lock (&global_nsm.lock) at:
  nsm_dev_ioctl+0x5f/0xcf [vuln_msv]
  but there are no more locks to release!
  no locks held by exploit/193.

Return immediately on the pre-lock copy_from_user() failure and keep the
common unlock label for the post-lock paths only.

Weakness: CWE-675 (Multiple Operations on Resource in Single-Operation Context)

## Which versions are affected by CVE-2026-68179?


## How do I fix CVE-2026-68179?

Apply the vendor's patch.

## Is CVE-2026-68179 being exploited?

There is no known exploitation of CVE-2026-68179 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-68179 and fix it if it is affected.

What it is: CVE-2026-68179 is a high-severity vulnerability in Linux, published on 10 Aug 2026. 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-2026-68179 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-2026-68179/ (Markdown: https://insights.sbomify.com/CVE-2026-68179/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-68179
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-68179
- OSV: https://osv.dev/vulnerability/CVE-2026-68179

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-68179/
Summaries are generated and may contain mistakes; the official description above is the record.