critical CVSS 9.4 EPSS 0.67%

CVE-2026-43114·Kernel vulnerability

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.

Severity
critical
Software
Kernel
Fixed in
6.19.14
Published

How likely is exploitation

FIRST's Exploit Prediction Scoring System puts the probability of this CVE being exploited in the next 30 days at 0.67% — higher than 50% of all published CVEs. EPSS is an independent forecast of exploitation, not a severity rating: it says nothing about how much damage a successful attack does, which is what a CVSS score measures.

Read the two together. CVE-2026-43114 scores 9.4 on CVSS, so a successful attack would be serious — but at 0.67%, almost nobody is currently attempting it. That is a different situation from a flaw under mass exploitation, and it is usually the difference between patching on your next maintenance window and patching tonight.

Affected versions

From: 6.19

Until: 6.19.14

Fixed in: 6.19.14

How to fix this CVE

Update your Linux kernel to version 6.19.14 or later to resolve a critical flaw in the netfilter AVX2 packet matching logic that causes incorrect element detection during pipapo set operations. This vulnerability affects firewall rule evaluation and network filtering accuracy. Reboot the system after applying the kernel update to ensure the patched version is active.

sudo dnf update kernel

Defensia detects this vulnerability

How to check if you are affected

  1. Step 1: Check your current kernel version with `uname -r` — verify if it falls between 6.19 and 6.19.14
  2. Step 2: Confirm netfilter is in use by running `lsmod | grep nf_tables` — if the module is loaded, the vulnerable code path is active
  3. Step 3: Search kernel logs for pipapo-related errors with `dmesg | grep -i pipapo` or `journalctl -b | grep -i pipapo` — look for set reloading failures or unexpected 'clashing element' messages
  4. Step 4: After applying the update, reboot and verify the new kernel version with `uname -r`, then re-check for netfilter module status with `lsmod | grep nf_tables`

FAQ

What is CVE-2026-43114?

This is a critical flaw in the Linux kernel's netfilter AVX2 implementation where the packet matching algorithm incorrectly returns expired or non-matching entries due to premature termination of the matching loop, causing firewall rules to be evaluated against wrong data.

Is CVE-2026-43114 being actively exploited?

No, there is no evidence of active exploitation or publicly available exploits at this time. However, the critical CVSS score of 9.4 warrants immediate patching due to the potential for integrity and availability impact.

What versions of Kernel are affected by CVE-2026-43114?

Linux kernel versions 6.19 through 6.19.13 are vulnerable. Version 6.19.14 and later contain the fix.

How do I check if my server is vulnerable to CVE-2026-43114?

Run `uname -r` to get your kernel version. If it shows 6.19.0 through 6.19.13, your system is vulnerable. Additionally, check if netfilter is active with `lsmod | grep nf_tables` — if pipapo sets are in use, the risk is higher.

Does Defensia detect CVE-2026-43114?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If Kernel is installed on a monitored server, CVE-2026-43114 will appear in your dashboard with remediation steps.

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References

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