CVE-2026-43114 netfilter: nft_set_pipapo_avx2: don't return non-matching entry on expiry
A logic error in the Linux kernel's AVX2 netfilter implementation causes incorrect set matching, leading to false positive duplicate entry errors during set reloads.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-43114?
CVE-2026-43114 is a critical vulnerability in Linux kernel, published on 6 May 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:
netfilter: nft_set_pipapo_avx2: don't return non-matching entry on expiry
New test case fails unexpectedly when avx2 matching functions are used.
The test first loads a ranomly generated pipapo set with 'ipv4 . port' key, i.e. nft -f foo.
This works. Then, it reloads the set after a flush: (echo flush set t s; cat foo) | nft -f -
This is expected to work, because its the same set after all and it was already loaded once.
But with avx2, this fails: nft reports a clashing element.
The reported clash is of following form:
We successfully re-inserted a . b c . d
Then we try to insert a . d
avx2 finds the already existing a . d, which (due to 'flush set') is marked as invalid in the new generation. It skips the element and moves to next.
Due to incorrect masking, the skip-step finds the next matching element *only considering the first field*,
i.e. we return the already reinserted "a . b", even though the last field is different and the entry should not have been matched.
No such error is reported for the generic c implementation (no avx2) or when the last field has to use the 'nft_pipapo_avx2_lookup_slow' fallback.
Bisection points to 7711f4bb4b36 ("netfilter: nft_set_pipapo: fix range overlap detection") but that fix merely uncovers this bug.
Before this commit, the wrong element is returned, but erronously reported as a full, identical duplicate.
The root-cause is too early return in the avx2 match functions. When we process the last field, we should continue to process data until the entire input size has been consumed to make sure no stale bits remain in the map.
Which versions are affected by CVE-2026-43114?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-43114?
Apply the vendor's patch.
Is CVE-2026-43114 being exploited?
There is no known exploitation of CVE-2026-43114 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2026-43114, DEBIAN-CVE-2026-43114, GHSA-6cwp-88hv-x237, ROOT-OS-DEBIAN-11-CVE-2026-43114, ROOT-OS-DEBIAN-12-CVE-2026-43114, ROOT-OS-UBUNTU-2204-CVE-2026-43114 and 2 more.