nfsd: fix fcache_disposal UAF by inlining dispose state into nfsd_net
CVE-2026-89682 · published 11 Sept 2026
How serious is it
- Severity: high, CVSS score 8.1 out of 10.
- No exploit prediction (EPSS) score yet.
- Not on the CISA list of exploited vulnerabilities.
- No public exploit in Exploit-DB.
Is your app affected by CVE-2026-89682?
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Who is affected
- Linux Linux: 1463b38e7cf34d4cc60f41daff459ad807b2e408 to < e6c3a43d0a41f03abae3764fc82a59369360c7e0, 1463b38e7cf34d4cc60f41daff459ad807b2e408 to < 9c8ac7c2b9b150e13b7ad0d0fae54f17747dce67, 1463b38e7cf34d4cc60f41daff459ad807b2e408 to < ba0ee9e04b7a0356c28d5a2fe445db675d24e572, 1463b38e7cf34d4cc60f41daff459ad807b2e408 to < cadc9036d5a8209f89e7026ddba7cfb1c716b03c
- Linux Linux: 5.17
How to check
- Find out whether you run the affected product and which version, then compare it with the versions above.
How to fix
Copies a prompt for Claude Code, Cursor or Codex that asks it to check whether you run this product.
- Apply the vendor's update or mitigation from the references below. If there is none yet, limit exposure of the affected service until there is.
- If a vulnerable version was live, check your logs and rotate the secrets that server could read.
The advisory
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.
Check your whole app
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References
- git.kernel.org/stable/c/e6c3a43d0a41f03abae3764fc82a59369360c7e0
- git.kernel.org/stable/c/9c8ac7c2b9b150e13b7ad0d0fae54f17747dce67
- git.kernel.org/stable/c/ba0ee9e04b7a0356c28d5a2fe445db675d24e572
- git.kernel.org/stable/c/cadc9036d5a8209f89e7026ddba7cfb1c716b03c
- git.kernel.org/stable/c/bbf13732f74351d21c5e0e8dd9bd8e1c48dc35d4
Merged from CVE List. Last updated 26 Oct 2026. All vulnerabilities · RSS · JSON