# CVE-2026-99172: ipc: drop the mqueue mount with kern_unmount() on setup failure


- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Fix available:** Yes
- **Published:** 28 Oct 2026
- **Updated:** 28 Oct 2026
- **Also known as:** AZL-111323, BELL-CVE-2026-99172, DEBIAN-CVE-2026-99172, GHSA-c64w-44gc-4h7w, UBUNTU-CVE-2026-99172

## What is CVE-2026-99172?

CVE-2026-99172 is a vulnerability in Linux, published on 28 Oct 2026. 

### Official description

In the Linux kernel, the following vulnerability has been resolved:

ipc: drop the mqueue mount with kern_unmount() on setup failure

mq_init_ns() creates the mqueue mount with fc_mount_longterm(), so its
->mnt_ns is MNT_NS_INTERNAL. When setting up the mqueue or ipc sysctls
or msg_init_ns() fails afterwards, create_ipc_ns() drops it with a plain
mntput(). With ->mnt_ns set that takes the fast path of
mntput_no_expire(). The count drops to zero and nothing ever kills the
mount, so the mount and the mqueue superblock are leaked.

Commit dc55e35f9e81 ("ipc: Store mqueue sysctls in the ipc namespace")
added the first failure path after mq_init_ns() and never dropped the
mount. Commit 7229d74e5e8c ("ipc: create_ipc_ns: drop mqueue mount on
sysctl setup failure") tried to fix that with a mntput() but that
doesn't help for a long-term mount.

Use kern_unmount(). free_ipc() open-codes the same thing for a namespace
that made it.

## Which versions are affected by CVE-2026-99172?


## How do I fix CVE-2026-99172?

Upgrade to a fixed version.

## Is CVE-2026-99172 being exploited?

There is no known exploitation of CVE-2026-99172 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-99172 and fix it if it is affected.

What it is: CVE-2026-99172 is a vulnerability in Linux, published on 28 Oct 2026. 
Exploitation: There is no known exploitation of CVE-2026-99172 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-2026-99172/ (Markdown: https://insights.sbomify.com/CVE-2026-99172/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-99172
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-99172
- OSV: https://osv.dev/vulnerability/CVE-2026-99172

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-99172/
Summaries are generated and may contain mistakes; the official description above is the record.