# CVE-2026-89714: NFS: fix delegation_hash_table leak when nfs4_server_common_setup() fails

> A memory leak in the Linux kernel NFS client allows local attackers to exhaust kernel memory by repeatedly failing NFSv4 mounts, causing denial of service.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 11 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** BELL-CVE-2026-89714, DEBIAN-CVE-2026-89714, GHSA-hv3g-87gw-4m9v, UBUNTU-CVE-2026-89714

## What is CVE-2026-89714?

CVE-2026-89714 is a memory corruption vulnerability in Linux, published on 11 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

In the Linux kernel, the following vulnerability has been resolved:

NFS: fix delegation_hash_table leak when nfs4_server_common_setup() fails

nfs4_server_common_setup() allocates server->delegation_hash_table
first, but server->destroy - the only path that frees the table via
nfs4_destroy_server() - is not assigned until the very end of the
function. If any intermediate step fails (the is_ds_only_client()
check, nfs4_init_session(), nfs4_get_rootfh(), or nfs_probe_server()),
the function returns with server->destroy still NULL, so the caller's
nfs_free_server() skips the destroy callback and the hash table is
leaked (4 KiB per attempt with the default delegation watermark).

This is trivially reachable from userspace: every failed NFSv4 mount
leaks one allocation. A client that persistently retries a mount that
cannot succeed leaks kernel memory without bound. Observed in
production where a Longhorn backup poller retried mount.nfs4 against
an NFSv3-only server roughly 10 times per second, leaking ~3.4 GiB of
unreclaimable slab (kmalloc-rnd-13-4k) per day; the node accumulated
12 GiB of leaked slab before the source was identified via the
kmem:kmalloc tracepoint (call_site=nfs4_delegation_hash_alloc).

Reproducer:

  # server exports NFSv3 only (or export path absent for v4)
  while :; do mount -t nfs4 <server>:/missing /mnt; done
  # watch SUnreclaim in /proc/meminfo grow 4 KiB per iteration

Free the table on the error paths between the allocation and the
assignment of server->destroy.

## Which versions are affected by CVE-2026-89714?


## How do I fix CVE-2026-89714?

Apply the vendor's patch.

## Is CVE-2026-89714 being exploited?

There is no known exploitation of CVE-2026-89714 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-89714 and fix it if it is affected.

What it is: CVE-2026-89714 is a memory corruption vulnerability in Linux, published on 11 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-89714 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-2026-89714/ (Markdown: https://insights.sbomify.com/CVE-2026-89714/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-89714
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-89714
- OSV: https://osv.dev/vulnerability/CVE-2026-89714

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-89714/
Summaries are generated and may contain mistakes; the official description above is the record.