# CVE-2026-97965: vxlan: initialize _md in vxlan_xmit_one()

> An attacker can leak uninitialized kernel stack data onto the network via VXLAN packets if specific metadata and GBP features are enabled.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 25 Sep 2026
- **Updated:** 21 Oct 2026
- **Also known as:** AZL-104600, BELL-CVE-2026-97965, DEBIAN-CVE-2026-97965, GHSA-qvvr-rf39-ch86, UBUNTU-CVE-2026-97965

## What is CVE-2026-97965?

CVE-2026-97965 is a vulnerability in Linux, published on 25 Sep 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:

vxlan: initialize _md in vxlan_xmit_one()

If a VXLAN device is configured with both VXLAN_F_COLLECT_METADATA and
VXLAN_F_GBP, and a packet is transmitted through it using an external
ip_tunnel_info that lacks the IP_TUNNEL_VXLAN_OPT_BIT flag, md is left
pointing to the uninitialized _md stack variable:

                if (test_bit(IP_TUNNEL_VXLAN_OPT_BIT, info->key.tun_flags)) {
                        if (info->options_len < sizeof(*md))
                                goto drop;
                        md = ip_tunnel_info_opts(info);
                }

Because IP_TUNNEL_VXLAN_OPT_BIT is not set, md is not updated and remains
pointing to _md. Later, vxlan_build_skb() is called with md, which
eventually calls vxlan_build_gbp_hdr():

        if (vxflags & VXLAN_F_GBP)
                vxlan_build_gbp_hdr(vxh, md);

Inside vxlan_build_gbp_hdr(), md->gbp is read:

        if (!md->gbp)
                return;
        gbp = (struct vxlanhdr_gbp *)vxh;
        ...
        if (md->gbp & VXLAN_GBP_DONT_LEARN)
                gbp->dont_learn = 1;

If the stack contains garbage, this causes:
1) VXLAN_HF_GBP flag to be spuriously set in the VXLAN header.
2) gbp->dont_learn and gbp->policy_applied to be set from stack bits.
3) gbp->policy_id to receive 16 bits of uninitialized kernel stack data,
   leaking it onto the wire.

Fix this by zero-initializing _md. If IP_TUNNEL_VXLAN_OPT_BIT is not
present, md->gbp remains 0, and vxlan_build_gbp_hdr() returns early
without modifying the VXLAN header.

## Which versions are affected by CVE-2026-97965?


## How do I fix CVE-2026-97965?

Apply the vendor's patch.

## Is CVE-2026-97965 being exploited?

There is no known exploitation of CVE-2026-97965 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-97965 and fix it if it is affected.

What it is: CVE-2026-97965 is a vulnerability in Linux, published on 25 Sep 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-2026-97965 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-2026-97965/ (Markdown: https://insights.sbomify.com/CVE-2026-97965/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-97965
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-97965
- OSV: https://osv.dev/vulnerability/CVE-2026-97965

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-97965/
Summaries are generated and may contain mistakes; the official description above is the record.