# CVE-2026-23304: ipv6: fix NULL pointer deref in ip6_rt_get_dev_rcu()

> A NULL pointer dereference in the Linux kernel IPv6 routing code can cause a system crash when a network device is un-slaved from a VRF.

- **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:** 25 Mar 2026
- **Updated:** 15 Oct 2026
- **Also known as:** AZL-80645, BELL-CVE-2026-23304, DEBIAN-CVE-2026-23304, GHSA-3qgv-qj84-5mmh, ROOT-OS-DEBIAN-11-CVE-2026-23304, ROOT-OS-DEBIAN-12-CVE-2026-23304, ROOT-OS-DEBIAN-13-CVE-2026-23304, ROOT-OS-UBUNTU-2204-CVE-2026-23304, ROOT-OS-UBUNTU-2404-CVE-2026-23304, UBUNTU-CVE-2026-23304

## What is CVE-2026-23304?

CVE-2026-23304 is a medium-severity vulnerability in Linux kernel, published on 25 Mar 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:

ipv6: fix NULL pointer deref in ip6_rt_get_dev_rcu()

l3mdev_master_dev_rcu() can return NULL when the slave device is being
un-slaved from a VRF. All other callers deal with this, but we lost
the fallback to loopback in ip6_rt_pcpu_alloc() -> ip6_rt_get_dev_rcu()
with commit 4832c30d5458 ("net: ipv6: put host and anycast routes on
device with address").

  KASAN: null-ptr-deref in range [0x0000000000000108-0x000000000000010f]
  RIP: 0010:ip6_rt_pcpu_alloc (net/ipv6/route.c:1418)
  Call Trace:
   ip6_pol_route (net/ipv6/route.c:2318)
   fib6_rule_lookup (net/ipv6/fib6_rules.c:115)
   ip6_route_output_flags (net/ipv6/route.c:2607)
   vrf_process_v6_outbound (drivers/net/vrf.c:437)

I was tempted to rework the un-slaving code to clear the flag first
and insert synchronize_rcu() before we remove the upper. But looks like
the explicit fallback to loopback_dev is an established pattern.
And I guess avoiding the synchronize_rcu() is nice, too.

Weakness: CWE-476 (NULL Pointer Dereference)

## Which versions are affected by CVE-2026-23304?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2026-23304?

Apply the vendor's patch.

## Is CVE-2026-23304 being exploited?

There is no known exploitation of CVE-2026-23304 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-2026-23304 and fix it if it is affected.

What it is: CVE-2026-23304 is a medium-severity vulnerability in Linux kernel, published on 25 Mar 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-2026-23304 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-2026-23304/ (Markdown: https://insights.sbomify.com/CVE-2026-23304/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-23304
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-23304
- OSV: https://osv.dev/vulnerability/CVE-2026-23304

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-23304/
Summaries are generated and may contain mistakes; the official description above is the record.