# CVE-2026-89685: nfsd: fix clock domain mismatch in clients_still_reclaiming()

> A clock domain mismatch in the Linux kernel NFS server allows attackers to indefinitely block non-reclaim operations, causing denial of service.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 11 Sep 2026
- **Updated:** 21 Oct 2026
- **Also known as:** AZL-100544, BELL-CVE-2026-89685, DEBIAN-CVE-2026-89685, GHSA-3574-3v33-rcrf, UBUNTU-CVE-2026-89685

## What is CVE-2026-89685?

CVE-2026-89685 is a high-severity denial of service vulnerability in Linux, published on 11 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

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.

## Which versions are affected by CVE-2026-89685?


## How do I fix CVE-2026-89685?

Apply the vendor's patch.

## Is CVE-2026-89685 being exploited?

There is no known exploitation of CVE-2026-89685 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-89685 and fix it if it is affected.

What it is: CVE-2026-89685 is a high-severity denial of service vulnerability in Linux, published on 11 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-89685 in the wild and no public exploit code.

Affected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-89685/ (Markdown: https://insights.sbomify.com/CVE-2026-89685/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-89685
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-89685
- OSV: https://osv.dev/vulnerability/CVE-2026-89685

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-89685/
Summaries are generated and may contain mistakes; the official description above is the record.