CVE-2026-99172 ipc: drop the mqueue mount with kern_unmount() on setup failure
- Exploited in the wild
- Not known
- Fix
- Available
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.
Sources
Also known as AZL-111323, BELL-CVE-2026-99172, DEBIAN-CVE-2026-99172, GHSA-c64w-44gc-4h7w, UBUNTU-CVE-2026-99172.