# CVE-2026-72254: netfilter: nft_fib: reject fib expression on the netdev egress hook

> A NULL pointer dereference in the Linux kernel netfilter module allows local attackers to cause a system crash by using specific FIB expressions on the netdev egress hook.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 15 Aug 2026
- **Updated:** 16 Oct 2026
- **Also known as:** BELL-CVE-2026-72254, DEBIAN-CVE-2026-72254, GHSA-f5p7-25h5-xxwh, UBUNTU-CVE-2026-72254

## What is CVE-2026-72254?

CVE-2026-72254 is a high-severity vulnerability in Linux, published on 15 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official 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.

## Which versions are affected by CVE-2026-72254?


## How do I fix CVE-2026-72254?

Apply the vendor's patch.

## Is CVE-2026-72254 being exploited?

There is no known exploitation of CVE-2026-72254 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-72254 and fix it if it is affected.

What it is: CVE-2026-72254 is a high-severity vulnerability in Linux, published on 15 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-72254 in the wild and no public exploit code.

Affected product: Linux. 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-2026-72254/ (Markdown: https://insights.sbomify.com/CVE-2026-72254/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-72254
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-72254
- OSV: https://osv.dev/vulnerability/CVE-2026-72254

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-72254/
Summaries are generated and may contain mistakes; the official description above is the record.