# CVE-2026-31428: netfilter: nfnetlink_log: fix uninitialized padding leak in NFULA_PAYLOAD

> A local attacker can read uninitialized kernel heap memory via the NFLOG netlink socket due to missing padding initialization in packet logging.

- **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:** 13 Apr 2026
- **Updated:** 15 Oct 2026
- **Also known as:** AZL-82724, BELL-CVE-2026-31428, DEBIAN-CVE-2026-31428, GHSA-mp33-36gg-v9h7, ROOT-OS-DEBIAN-11-CVE-2026-31428, ROOT-OS-DEBIAN-12-CVE-2026-31428, ROOT-OS-DEBIAN-13-CVE-2026-31428, ROOT-OS-UBUNTU-2204-CVE-2026-31428, ROOT-OS-UBUNTU-2404-CVE-2026-31428, UBUNTU-CVE-2026-31428

## What is CVE-2026-31428?

CVE-2026-31428 is a medium-severity vulnerability in Linux kernel, published on 13 Apr 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: fix uninitialized padding leak in NFULA_PAYLOAD

__build_packet_message() manually constructs the NFULA_PAYLOAD netlink
attribute using skb_put() and skb_copy_bits(), bypassing the standard
nla_reserve()/nla_put() helpers. While nla_total_size(data_len) bytes
are allocated (including NLA alignment padding), only data_len bytes
of actual packet data are copied. The trailing nla_padlen(data_len)
bytes (1-3 when data_len is not 4-byte aligned) are never initialized,
leaking stale heap contents to userspace via the NFLOG netlink socket.

Replace the manual attribute construction with nla_reserve(), which
handles the tailroom check, header setup, and padding zeroing via
__nla_reserve(). The subsequent skb_copy_bits() fills in the payload
data on top of the properly initialized attribute.

Weakness: CWE-908 (Use of Uninitialized Resource)

## Which versions are affected by CVE-2026-31428?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-31428?

Apply the vendor's patch.

## Is CVE-2026-31428 being exploited?

There is no known exploitation of CVE-2026-31428 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-2026-31428 and fix it if it is affected.

What it is: CVE-2026-31428 is a medium-severity vulnerability in Linux kernel, published on 13 Apr 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-2026-31428 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-2026-31428/ (Markdown: https://insights.sbomify.com/CVE-2026-31428/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-31428
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-31428
- OSV: https://osv.dev/vulnerability/CVE-2026-31428

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-31428/
Summaries are generated and may contain mistakes; the official description above is the record.