# CVE-2026-64580: xfrm6: clear dst.dev on error to avoid double netdev_put in xfrm6_fill_dst()

> A double free of a network device reference in the Linux kernel XFRM6 subsystem can cause a refcount underflow and system instability.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/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:** 5 Aug 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-94464, BELL-CVE-2026-64580, DEBIAN-CVE-2026-64580, GHSA-g6rx-f8gv-c53j, UBUNTU-CVE-2026-64580

## What is CVE-2026-64580?

CVE-2026-64580 is a high-severity use after free vulnerability in Linux, published on 5 Aug 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:

xfrm6: clear dst.dev on error to avoid double netdev_put in xfrm6_fill_dst()

On the error path where in6_dev_get(dev) returns NULL, xfrm6_fill_dst()
releases the device reference with netdev_put() but leaves
xdst->u.dst.dev set. dst_destroy() later calls netdev_put(dst->dev)
again, so the same net_device reference is released twice, underflowing
its refcount (ref_tracker WARNING + "unregister_netdevice: waiting for
<dev> to become free").

Clear xdst->u.dst.dev after the netdev_put(), the same way the XFRM
device-offload paths xfrm_dev_state_add() and xfrm_dev_policy_add() in
net/xfrm/xfrm_device.c NULL ->dev when releasing the reference on error.

  ref_tracker: reference already released.
  ref_tracker: allocated in:
   xfrm6_fill_dst (net/ipv6/xfrm6_policy.c:86)
   ...
   udpv6_sendmsg (net/ipv6/udp.c:1696)
   ...
  ref_tracker: freed in:
   xfrm6_fill_dst (net/ipv6/xfrm6_policy.c:90)
   ...
  WARNING: lib/ref_tracker.c:322 at ref_tracker_free+0x58b/0x780
   dst_destroy (net/core/dst.c:115)
   rcu_core
   handle_softirqs
   ...

Weakness: CWE-415 (Double Free)

## Which versions are affected by CVE-2026-64580?


## How do I fix CVE-2026-64580?

Apply the vendor's patch.

## Is CVE-2026-64580 being exploited?

There is no known exploitation of CVE-2026-64580 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-64580 and fix it if it is affected.

What it is: CVE-2026-64580 is a high-severity use after free vulnerability in Linux, published on 5 Aug 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-2026-64580 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-2026-64580/ (Markdown: https://insights.sbomify.com/CVE-2026-64580/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-64580
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-64580
- OSV: https://osv.dev/vulnerability/CVE-2026-64580

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-64580/
Summaries are generated and may contain mistakes; the official description above is the record.