CVE-2026-31418
MediumCVSS 5.5Exploitation Probability (EPSS)
Low risk2th percentile - higher than 2% of all known CVEs
Summary
In the Linux kernel, in the netfilter: ipset subsystem, a vulnerability was found in the mtype_del function that incorrectly handles logically empty buckets. The function failed to release a bucket when all entries were removed but the n->pos pointer still pointed past deleted slots.
Risk Assessment
This vulnerability may cause kernel memory leaks and inefficient IP set management, potentially leading to denial of service (DoS) by exhausting system resources.
Recommendation
Immediately update the Linux kernel to a version containing the fix (commit in the netfilter repository). Monitor security advisories from your Linux distribution and apply the patch once released.
Original NVD description (English source)
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.