# CVE-2026-43026: netfilter: ctnetlink: zero expect NAT fields when CTA_EXPECT_NAT absent

> An attacker can read stale kernel memory via netlink dumps when NAT fields are uninitialized, potentially exposing sensitive data.

- **Severity:** Medium 5.5 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 1 May 2026
- **Updated:** 15 Oct 2026
- **Also known as:** BELL-CVE-2026-43026, DEBIAN-CVE-2026-43026, GHSA-x32p-2gcj-5qgh, ROOT-OS-DEBIAN-11-CVE-2026-43026, ROOT-OS-UBUNTU-2204-CVE-2026-43026, ROOT-OS-UBUNTU-2404-CVE-2026-43026, UBUNTU-CVE-2026-43026

## What is CVE-2026-43026?

CVE-2026-43026 is a medium-severity vulnerability in Linux kernel, published on 1 May 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official 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.

## Which versions are affected by CVE-2026-43026?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-43026?

Apply the vendor's patch.

## Is CVE-2026-43026 being exploited?

There is no known exploitation of CVE-2026-43026 in the wild and no public exploit code.

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-43026 and fix it if it is affected.

What it is: CVE-2026-43026 is a medium-severity vulnerability in Linux kernel, published on 1 May 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-43026 in the wild and no public exploit code.

Affected product: Linux kernel. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-43026/ (Markdown: https://insights.sbomify.com/CVE-2026-43026/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-43026
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-43026
- OSV: https://osv.dev/vulnerability/CVE-2026-43026

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-43026/
Summaries are generated and may contain mistakes; the official description above is the record.