CVE-2026-43114 — netfilter: nft_set_pipapo_avx2: don't return non-matching entry on expiry

Affected: Linux, Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 10.0 Extended Update Support, Red Hat Enterprise Linux 9, Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions, Red Hat Enterprise Linux 9.4 Update Services for SAP Solutions, Red Hat Enterprise Linux 9.6 Extended Update Support, Red Hat OpenShift Container Platform 4.20, Red Hat OpenShift Container Platform 4.21, Red Hat OpenShift Container Platform 4.22 and 3 more

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 r…

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CVE-2026-43114 — netfilter: nft_set_pipapo_avx2: don't return non-matching entry on expiry