# CVE-2026-98851: netfilter: nft_flow_offload: drop flowtable reference on init error path

> A reference leak in the Linux kernel netfilter flow offload allows attackers to prevent flowtable removal, causing a 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:** 18 Oct 2026
- **Updated:** 21 Oct 2026
- **Also known as:** AZL-109341, BELL-CVE-2026-98851, DEBIAN-CVE-2026-98851, GHSA-95vh-jxqc-h2w9, UBUNTU-CVE-2026-98851

## What is CVE-2026-98851?

CVE-2026-98851 is a denial of service vulnerability in Linux, published on 18 Oct 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:

netfilter: nft_flow_offload: drop flowtable reference on init error path

nft_flow_offload_init() bumps the flowtable use count with
nft_use_inc() before calling nf_ct_netns_get().  When the latter
fails, the error is returned as-is and the reference is leaked.

The upper layers do not balance it either: nf_tables_newexpr()
clears expr->ops when the expression init callback fails, so the
nft_expr_more() iteration in nft_rule_expr_deactivate() and
nf_tables_rule_destroy() stops right before the failed expression
and its ->destroy callback, which would drop the reference, never
runs.

Each failed rule addition therefore leaks one flowtable reference
and the flowtable can no longer be removed: NFT_MSG_DELFLOWTABLE
keeps reporting -EBUSY even though no rule references it.

Save the nf_ct_netns_get() return value and undo the nft_use_inc()
when it fails, restoring the inc/dec pairing within
nft_flow_offload_init() itself.

## Which versions are affected by CVE-2026-98851?


## How do I fix CVE-2026-98851?

Apply the vendor's patch.

## Is CVE-2026-98851 being exploited?

There is no known exploitation of CVE-2026-98851 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98851 and fix it if it is affected.

What it is: CVE-2026-98851 is a denial of service vulnerability in Linux, published on 18 Oct 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-2026-98851 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-2026-98851/ (Markdown: https://insights.sbomify.com/CVE-2026-98851/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98851
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98851
- OSV: https://osv.dev/vulnerability/CVE-2026-98851

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98851/
Summaries are generated and may contain mistakes; the official description above is the record.