---
id: "CVE-2026-99172"
kind: "vulnerability"
aliases: ["CVE-2026-99172"]
title: "Linux kernel: failed IPC namespace setup leaks the mqueue mount"
severity: "low"
cvss: null
epss: null
exploited: false
status: "open"
category: "runtime"
products: []
ecosystems: []
tags: ["containers", "linux-kernel", "runtime"]
not_affected_if: ["no-ipc-namespaces"]
published_at: "2026-10-28T11:17:37+00:00"
first_seen_at: "2026-10-28T11:32:36+00:00"
updated_at: "2026-10-28T11:35:34+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-99172", "first_seen_at": "2026-10-28T11:32:36+00:00"}]
---

# Linux kernel: failed IPC namespace setup leaks the mqueue mount

When creating an IPC namespace fails partway through setup, the kernel drops the mqueue mount with a plain mntput(), which does not actually release a long-term mount. The mount and its mqueue superblock are leaked, so the failure path wastes kernel memory.

_Summary, check and fix written by a model from the sources; labelled as such._

## Timeline

- 2026-10-28T11:32:36+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-99172

## From the sources

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.

---

_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_