# CVE-2026-98484: netfilter: nf_tables: skip expired catchall elements on insert and delete

> Expired netfilter catchall elements cause silent rule failures and deletion errors, leading to potential denial of service in Linux kernel networking.

- **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-108665, BELL-CVE-2026-98484, DEBIAN-CVE-2026-98484, GHSA-j4h7-w628-h5g3, UBUNTU-CVE-2026-98484

## What is CVE-2026-98484?

CVE-2026-98484 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: nf_tables: skip expired catchall elements on insert and delete

nft_setelem_catchall_insert() looks up duplicates with
nft_set_elem_active() only, while nft_set_catchall_lookup() and the
dump path additionally skip expired elements.

Once a catchall element with a timeout expires, this predicate drift
makes it invisible to userspace dumps, yet it still blocks
re-insertion: with NLM_F_EXCL the request fails with -EEXIST, and
without it the request reports success but silently inserts nothing.
The stale entry only goes away when the (user-tunable) gc interval
elapses, so the catchall rule may silently stop matching for an
arbitrarily long time after its first expiration.

The delete path shows the same drift: nft_setelem_catchall_deactivate()
picks the first active-next entry in the catchall list, so with an
expired entry still pending GC it retires the stale entry instead of
the fresh one, and it deactivates an element that userspace no longer
sees instead of failing with -ENOENT.

Align both walks with the lookup and dump predicates: only an element
that is active and not expired counts as a duplicate or delete
candidate, using the per-netns timestamp taken at transaction start,
in line with the set backend .insert/.deactivate and catchall GC sync
paths.

## Which versions are affected by CVE-2026-98484?


## How do I fix CVE-2026-98484?

Apply the vendor's patch.

## Is CVE-2026-98484 being exploited?

There is no known exploitation of CVE-2026-98484 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98484 and fix it if it is affected.

What it is: CVE-2026-98484 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-2026-98484 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-2026-98484/ (Markdown: https://insights.sbomify.com/CVE-2026-98484/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98484
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98484
- OSV: https://osv.dev/vulnerability/CVE-2026-98484

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98484/
Summaries are generated and may contain mistakes; the official description above is the record.