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.
- 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
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.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-98484 being exploited?
There is no known exploitation of CVE-2026-98484 in the wild and no public exploit code.
Sources
Also known as AZL-108665, BELL-CVE-2026-98484, DEBIAN-CVE-2026-98484, GHSA-j4h7-w628-h5g3, UBUNTU-CVE-2026-98484.