Bug 2457831 (CVE-2026-31418)

Summary: CVE-2026-31418 kernel: netfilter: ipset: drop logically empty buckets in mtype_del
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
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OS: Linux   
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Description OSIDB Bzimport 2026-04-13 14:01:57 UTC 
In the Linux kernel, the following vulnerability has been resolved:

netfilter: ipset: drop logically empty buckets in mtype_del

mtype_del() counts empty slots below n->pos in k, but it only drops the
bucket when both n->pos and k are zero. This misses buckets whose live
entries have all been removed while n->pos still points past deleted slots.

Treat a bucket as empty when all positions below n->pos are unused and
release it directly instead of shrinking it further.
Comment 1 Alexander B 2026-04-14 10:20:28 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026041311-CVE-2026-31418-e6b9@gregkh/T