# CVE-2026-43085: netfilter: nfnetlink_log: initialize nfgenmsg in NLMSG_DONE terminator

> A Linux kernel netfilter bug leaks stale kernel heap data to userspace via uninitialized netlink message terminators, allowing local attackers to read sensitive memory.

- **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:** 6 May 2026
- **Updated:** 15 Oct 2026
- **Also known as:** BELL-CVE-2026-43085, DEBIAN-CVE-2026-43085, GHSA-rp69-c9w2-rv4p, ROOT-OS-DEBIAN-11-CVE-2026-43085, ROOT-OS-DEBIAN-12-CVE-2026-43085, ROOT-OS-UBUNTU-2204-CVE-2026-43085, ROOT-OS-UBUNTU-2404-CVE-2026-43085, UBUNTU-CVE-2026-43085

## What is CVE-2026-43085?

CVE-2026-43085 is a medium-severity vulnerability in Linux kernel, published on 6 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: nfnetlink_log: initialize nfgenmsg in NLMSG_DONE terminator

When batching multiple NFLOG messages (inst->qlen > 1), __nfulnl_send()
appends an NLMSG_DONE terminator with sizeof(struct nfgenmsg) payload via
nlmsg_put(), but never initializes the nfgenmsg bytes. The nlmsg_put()
helper only zeroes alignment padding after the payload, not the payload
itself, so four bytes of stale kernel heap data are leaked to userspace
in the NLMSG_DONE message body.

Use nfnl_msg_put() to build the NLMSG_DONE terminator, which initializes
the nfgenmsg payload via nfnl_fill_hdr(), consistent with how
__build_packet_message() already constructs NFULNL_MSG_PACKET headers.

## Which versions are affected by CVE-2026-43085?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-43085?

Apply the vendor's patch.

## Is CVE-2026-43085 being exploited?

There is no known exploitation of CVE-2026-43085 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-2026-43085 and fix it if it is affected.

What it is: CVE-2026-43085 is a medium-severity vulnerability in Linux kernel, published on 6 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-2026-43085 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-2026-43085/ (Markdown: https://insights.sbomify.com/CVE-2026-43085/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-43085
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-43085
- OSV: https://osv.dev/vulnerability/CVE-2026-43085

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-43085/
Summaries are generated and may contain mistakes; the official description above is the record.