nfsd: fix clock domain mismatch in clients_still_reclaiming()
CVE-2026-89685 · published 11 Sept 2026
How serious is it
- Severity: high, CVSS score 7.5 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-2026-89685?
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Who is affected
- Linux Linux: 20b7d86f29d39e8ae19bb29c24ffee70dc385ddf to < 04c3e4456fe76e8d7c94171009df3165c3262c51, 20b7d86f29d39e8ae19bb29c24ffee70dc385ddf to < e92e80c5b043108029bc729b30d12c37158fb9cb, 20b7d86f29d39e8ae19bb29c24ffee70dc385ddf to < f9cec313efb2fd18d962aad738a4892bce806016, 20b7d86f29d39e8ae19bb29c24ffee70dc385ddf to < 9843649196221152b6e5d138a3ce859bdaae1d96
- Linux Linux: 5.6
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 clock domain mismatch in clients_still_reclaiming()
clients_still_reclaiming() computes a deadline from nn->boot_time
(CLOCK_REALTIME, ~1.7 billion) but compares it against
ktime_get_boottime_seconds() (CLOCK_BOOTTIME, seconds since boot).
The comparison is always false — it would take ~54 years of uptime
for BOOTTIME to exceed the REALTIME-derived deadline.
This means any client can hold the server in grace indefinitely by
sending CLAIM_PREVIOUS OPEN requests, blocking all non-reclaim
operations for all other clients.
Add boot_time_bt (CLOCK_BOOTTIME) alongside the existing boot_time
and use it for the deadline computation. boot_time (CLOCK_REALTIME)
is preserved for its cl_boot clientid-nonce role.
Check your whole app
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References
- git.kernel.org/stable/c/04c3e4456fe76e8d7c94171009df3165c3262c51
- git.kernel.org/stable/c/e92e80c5b043108029bc729b30d12c37158fb9cb
- git.kernel.org/stable/c/f9cec313efb2fd18d962aad738a4892bce806016
- git.kernel.org/stable/c/9843649196221152b6e5d138a3ce859bdaae1d96
- git.kernel.org/stable/c/09ea3eb9a518565f5bca386e81b993ed8825f5e8
Merged from CVE List. Last updated 26 Oct 2026. All vulnerabilities · RSS · JSON