CVE-2026-43114
CriticalCVSS 9.4Exploitation Probability (EPSS)
Low risk27th percentile — higher than 27% of all known CVEs
Summary
In the Linux kernel, the AVX2 implementation for netfilter pipapo sets has a bug that returns non-matching entries on expiry. The issue occurs when AVX2 match functions prematurely stop processing the last field, leaving stale bits in the map, leading to false element clash reports.
Risk Assessment
Organizations may experience incorrect netfilter rule behavior, including false conflicts when inserting elements into pipapo sets, potentially leading to firewall misconfiguration and security gaps.
Recommendation
Immediately update the Linux kernel to a version containing the fix (commit 7711f4bb4b36 or later). As a workaround, disable AVX2 for netfilter using the kernel parameter 'nft_set_pipapo_avx2=0'.
Original NVD description (English source)
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.